# Fiber Optic communication MCQ Questions And Answers

1. Who proposed the idea of transmission of light via dielectric waveguide structure?
a) Christian Huygens
b) Karpon and Bockham
c) Hondros and debye
d) Albert Einstein

2. Who proposed the use of clad waveguide structure?
a) Edward Appleton
b) Schriever
c) Kao and Hockham
d) James Maxwell
Answer : – c) Kao and Hockham

3. Which law gives the relationship between refractive index of the dielectric?
a) Law of reflection
b) Law of refraction (Snell’s Law)
c) Millman’s Law
d) Huygen’s Law

4. The light sources used in fibre optics communication are ____________
a) LED’s and Lasers
b) Phototransistors
c) Xenon lights
d) Incandescent
Answer: –  b) Law of refraction (Snell’s Law)

5. The ________ ray passes through the axis of the fiber core.
a) Reflected
b) Refracted
c) Meridional
d) Shew

6. Light incident on fibers of angles________the acceptance angle do not propagate into the fiber.
a) Less than
b) Greater than
c) Equal to
d) Less than and equal to

7. What is the numerical aperture of the fiber if the angle of acceptance is 16 degree?
a) 0.50
b) 0.36
c) 0.20
d) 0.27

8. The ratio of speed of light in air to the speed of light in another medium is called as _________
a) Speed factor
b) Dielectric constant
c) Reflection index
d) Refraction index

9. When a ray of light enters one medium from another medium, which quality will not change?
a) Direction
b) Frequency
c) Speed
d) Wavelength

1. Which equations are best suited for the study of electromagnetic wave propagation?
a) Maxwell’s equations
b) Allen-Cahn equations
c) Avrami equations
d) Boltzmann’s equations

2. When λ is the optical wavelength in vacuum, k is given by k=2Π/λ. What does k stand for in the above equation?
a) Phase propagation constant
b) Dielectric constant
c) Boltzmann’s constant
d) Free-space constant

3. Constructive interference occur when total phase change after two successive reflections at upper and lower interfaces is equal to? (Where m is integer)
a) 2Πm
b) Πm
c) Πm/4
d) Πm/6

4. When light is described as an electromagnetic wave, it consists of a periodically varying electric E and magnetic field H which are oriented at an angle?
a) 90 degree to each other
b) Less than 90 degree
c) Greater than 90 degree
d) 180 degree apart
Answer: a) 90 degree to each other

5. A monochromatic wave propagates along a waveguide in z direction. These points of constant phase travel in constant phase travel at a phase velocity Vp is given by?
a) Vp=ω/β
b) Vp=ω/c
c) Vp=C/N
d) Vp=mass/acceleration

6. Which is the most important velocity in the study of transmission characteristics of optical fiber?
a) Phase velocity
b) Group velocity
c) Normalized velocity
d) Average velocity

7. What is refraction?
a) Bending of light waves
b) Reflection of light waves
c) Diffusion of light waves
d) Refraction of light waves
Answer:  a) Bending of light waves

8. The phenomenon which occurs when an incident wave strikes an interface at an angle greater than the critical angle with respect to the normal to the surface is called as ____________
a) Refraction
b) Partial internal reflection
c) Total internal reflection
d) Limiting case of refraction

1. A multimode step index fiber has a normalized frequency of 72. Estimate the number of guided modes.
a) 2846
b) 2592
c) 2432
d) 2136

2. A graded-index fiber has a core with parabolic refractive index profile of diameter of 30μm, NA=0.2, λ=1μm. Estimate the normalised frequency.
a) 19.32
b) 18.84
c) 16.28
d) 17.12

3. A step-index fiber has core refractive index 1.46 and radius 4.5μm. Find the cutoff wavelength to exhibit single mode operation. Use relative index difference as 0.25%.
a) 1.326μm
b) 0.124μm
c) 1.214μm
d) 0.123μm

4. A single-mode step-index fiber or multimode step-index fiber allows propagation of only one transverse electromagnetic wave.
a) True
b) False

5. One of the given statements is true for intermodal dispersion. Choose the right one.
a) Low in single mode and considerable in multimode fiber
b) Low in both single mode and multimode fiber
c) High in both single mode and multimode fiber
d) High in single mode and low in multimode fiber
Answer: a) Low in single mode and considerable in multimode fiber

6. For lower bandwidth applications ______________

a) Single mode fiber is advantageous
b) Photonic crystal fibers are advantageous

7. Most of the optical power is carried out in core region than in cladding.
a) True
b) False

a) Straight path along the axis
b) Curved path along the axis
c) Path where rays changes angles at core-cladding interface
d) Helical path
Answer: b) Curved path along the axis

9. What is the unit of normalized frequency?
a) Hertz
b) Meter/sec
c) Coulombs
d) It is a dimensionless quantity
Answer: d) It is a dimensionless quantity

10. Skew rays follow a ___________
a) Hyperbolic path along the axis
b) Parabolic path along the axis
c) Helical path
d) Path where rays changes angles at core-cladding interface

1. An optical fiber has core-index of 1.480 and a cladding index of 1.478. What should be the core size for single mode operation at 1310nm?
a) 7.31μm
b) 8.71μm
c) 5.26μm
d) 6.50μm

2. An optical fiber has a core radius 2μm and a numerical aperture of 0.1. Will this fiber operate at single mode at 600 nm?
a) Yes
b) No

3. What is needed to predict the performance characteristics of single mode fibers?
a) The intermodal delay effect
b) Geometric distribution of light in a propagating mode
c) Fractional power flow in the cladding of fiber
d) Normalized frequency
Answer: b) Geometric distribution of light in a propagating mode

4. Which equation is used to calculate MFD?
a) Maxwell’s equations
b) Peterman equations
c) Allen Cahn equations
d) Boltzmann’s equations

5. A single mode fiber has mode field diameter 10.2μm and V=2.20. What is the core diameter of this fiber?
a) 11.1μm
b) 13.2μm
c) 7.6μm
d) 10.1μm

6. The difference between the modes’ refractive indices is called as ___________
a) Polarization
b) Cutoff
c) Fiber birefringence
d) Fiber splicing

7. A single mode fiber has a beat length of 4cm at 1200nm. What is birefringence?
a) 2*10-5
b) 1.2*10-5
c) 3*10-5
d) 2

8. How many propagation modes are present in single mode fibers?
a) One
b) Two
c) Three
d) Five

9. Numerical aperture is constant in case of step index fiber.
a) True
b) False

10. Plastic fibers are less widely used than glass fibers.
a) True
b) False

1. Photonic crystal fibers also called as ___________
a) Conventional fibers
b) Dotted fibers
c) Stripped fibers
d) Holey fibers

2. Conventional optical fibers has more transmission losses than photonic crystal fibers.
a) True
b) False

3. Losses in photonic crystal fibers are reduced to a level of ___________
a) 0.1dB/km
b) 0.2dB/km
c) 0.3dB/km
d) 0.4dB/km

4. The high index contrast enables the PCF core to be reduced from around 8 μmin conventional fiber to ___________
a) Less than 1μm
b) More than 5μm
c) More than 3μm
d) More than 2μm

5. The periodic arrangement of cladding air holes in photonic band gap fibers provides for the formation of a photonic band gap in the ___________
a) H-plane of fiber
b) E-plane of fiber
c) E-H-plane of fiber
d) Transverse plane of fiber
Answer: d) Transverse plane of fiber

6. In index-guided photonic crystal fiber structure, the dark areas are air holes. What does white areas suggests?
a) Air
b) Silica
c) Water
d) Plasma

7. Which is the unit of measurement of attenuation in optical fibers?
a) km
b) dB
c) dB/km
d) Coulomb’s

8. The optical fiber incurs a loss in signal power as light travels down the fiber which is called as ___________
a) Scattering
b) Attenuation
c) Absorption
d) Refraction

9. If the input power 100μW is launched into 6 km of fiber, the mean optical power at the fiber output is 2μW. What is the overall signal attenuation through the fiber assuming there are no connectors or splices?
a) 15.23dB
b) 16.98dB
c) 17.12dB
d) 16.62dB

10. A device that reduces the intensity of light in optical fiber communications is ___________
a) compressor
b) Optical attenuator
c) Barometer
d) Reducer

11. A decibel may be defined as the ratio of input and output optical power for a particular optical wavelength.
a) True
b) False

12. When the input and output power in an optical fiber is 120μW & 3μW respectively and the length of the fiber is 8 km. What is the signal attenuation per km for the fiber?
a) 3dB/km
b) 2dB/km
c) 1dB/km
d) 4dB/km

1. Which of the following statements best explain the concept of material absorption?
a) A loss mechanism related to the material composition and fabrication of fiber
b) A transmission loss for optical fibers
c) Results in attenuation of transmitted light
d) Causes of transfer of optical power
Answer: a) A loss mechanism related to the material composition and fabrication of fiber

2. How many mechanisms are there which causes absorption?
a) One
b) Three
c) Two
d) Four

3. Absorption losses due to atomic defects mainly include ___________
b) Missing molecules, oxygen defects in glass
c) Impurities in fiber material
d) Interaction with other components of core
Answer: b) Missing molecules, oxygen defects in glass

4. The effects of intrinsic absorption can be minimized by ___________
a) Ionization
c) Suitable choice of core and cladding components
d) Melting

5. Which of the following is not a metallic impurity found in glass in extrinsic absorption?
a) Fe2+
b) Fe3+
c) Cu
d) Si

6. Optical fibers suffer radiation losses at bends or curves on their paths.
a) True
b) False

7. In the given equation, state what αr suggests?
b) Refractive index difference
d) Constant of proportionality

8. A multimode fiber has refractive indices n1 = 1.15, n2 = 1.11 and an operating wavelength of 0.7μm. Find the radius of curvature?
a) 8.60μm
b) 9.30μm
c) 9.1μm
d) 10.2μm

9. A single mode fiber has refractive indices n1=1.50, n2 = 2.23, core diameter of 8μm, wavelength = 1.5μm cutoff wavelength = 1.214μm. Find the radius of curvature?
a) 12 mm
b) 20 mm
c) 34 mm
d) 36 mm

10. How the potential macro bending losses can be reduced in case of multimode fiber?
a) By designing fibers with large relative refractive index differences
b) By maintaining direction of propagation
c) By reducing the bend
d) By operating at larger wavelengths
Answer: a) By designing fibers with large relative refractive index differences

11. Sharp bends or micro bends causes significant losses in fiber.
a) True
b) False

1. Rayleigh scattering and Mie scattering are the types of _____________
a) Linear scattering losses
b) Non-linear scattering losses
c) Fiber bends losses
d) Splicing losses

2. Dominant intrinsic loss mechanism in low absorption window between ultraviolet and infrared absorption tails is ___________
a) Mie scattering
b) Rayleigh scattering
c) Stimulated Raman scattering
d) Stimulated Brillouin scattering

3. Rayleigh scattering can be reduced by operating at smallest possible wavelengths.
a) True
b) False

4. The scattering resulting from fiber imperfections like core-cladding RI differences, diameter fluctuations, strains, and bubbles is?
a) Rayleigh scattering
b) Mie scattering
c) Stimulated Brillouin scattering
d) Stimulated Raman scattering

5. Mie scattering has in-homogeneities mainly in ___________
a) Forward direction
b) Backward direction
c) All direction

6. The in-homogeneities in Mie scattering can be reduced by coating of a fiber.
a) True
b) False

7. Raman and Brillouin scattering are usually observed at ___________
a) Low optical power densities
b) Medium optical power densities
c) High optical power densities
d) Threshold power densities
Answer : c) High optical power densities

8. The phonon is a quantum of an elastic wave in a crystal lattice.
a) True
b) False

9. A single-mode optical fiber has an attenuation of 0.3dB/km when operating at wavelength of 1.1μm. The fiber core diameter is 4μm and bandwidth is 500 MHz. Find threshold optical power for stimulated Brillouin scattering.
a) 11.20 mw
b) 12.77 mw
c) 13.08 mw
d) 12.12 mw

10. 0.4 dB/km, 1.4μm, 6μm, 550MHz. Find threshold optical power for stimulated Raman scattering.
a) 1.98 W
b) 1.20 W
c) 1.18 W
d) 0.96 W

11. Stimulated Brillouin scattering is mainly a ___________
a) Forward process
b) Backward process
c) Upward process
d) Downward process

12. High frequency optical phonon is generated in stimulated Raman scattering.
a) False
b) True

13. Stimulated Raman scattering occur in ___________
a) Forward direction
b) Backward direction
c) Upward direction
d) Forward and backward direction
Answer: d) Forward and backward direction

14. Stimulated Raman scattering may have an optical power threshold of may be three orders of magnitude ___________
a) Lower than Brillouin threshold
b) Higher than Brillouin threshold
c) Same as Brillouin threshold
d) Higher than Rayleigh threshold
Answer: b) Higher than Brillouin threshold

1. What is dispersion in optical fiber communication?
a) Compression of light pulses
b) Broadening of transmitted light pulses along the channel
c) Overlapping of light pulses on compression
d) Absorption of light pulses

2. What does ISI stand for in optical fiber communication?
a) Invisible size interference
b) Infrared size interference
c) Inter-symbol interference
d) Inter-shape interference

3. For no overlapping of light pulses down on an optical fiber link, the digital bit rate BT must be ___________
a) Less than the reciprocal of broadened pulse duration
b) More than the reciprocal of broadened pulse duration
c) Same as that of than the reciprocal of broadened pulse duration
d) Negligible

4. The maximum bit rate that may be obtained on an optical fiber link is 1/3Γ.
a) True
b) False

5. 3dB optical bandwidth is always ___________ the 3dB electrical bandwidth.
a) Smaller than
b) Larger than
c) Negligible than
d) Equal to

6. A multimode graded index fiber exhibits a total pulse broadening of 0.15μsover a distance of 16 km. Estimate the maximum possible bandwidth, assuming no intersymbol interference.
a) 4.6 MHz
b) 3.9 MHz
c) 3.3 MHz
d) 4.2 MHz

7. What is pulse dispersion per unit length if for a graded index fiber, 0.1μs pulse broadening is seen over a distance of 13 km?
a) 6.12ns/km
b) 7.69ns/km
c) 10.29ns/km
d) 8.23ns/km

8. Chromatic dispersion is also called as intermodal dispersion.
a) True
b) False

9. Chromatic dispersion is also called as intermodal dispersion.
a) True
b) False

10. The optical source used in a fiber is an injection laser with a relative spectral width σλ/λ of 0.0011 at a wavelength of 0.70μm. Estimate the RMS spectral width.
a) 1.2 nm
b) 1.3 nm
c) 0.77 nm
d) 0.98 nm

11. In waveguide dispersion, refractive index is independent of ______________
a) Bit rate
b) Index difference
c) Velocity of medium
d) Wavelength

1. Intermodal dispersion occurring in a large amount in multimode step index fiber results in ____________
a) Propagation of the fiber
b) Propagating through the fiber
d) Attenuation of waves

2. After Total Internal Reflection the Meridional ray __________
a) Makes an angle equal to acceptance angle with the axial ray
b) Makes an angle equal to critical angle with the axial ray
c) Travels parallel equal to critical angle with the axial ray
d) Makes an angle equal to critical angle with the axial ray
Answer: d) Makes an angle equal to critical angle with the axial ray

3. Consider a single mode fiber having core refractive index n1= 1.5. The fiber length is 12m. Find the time taken by the axial ray to travel along the fiber.
a) 1.00μsec
b) 0.06μsec
c) 0.90μsec
d) 0.30μsec

4. A 4 km optical link consists of multimode step index fiber with core refractive index of 1.3 and a relative refractive index difference of 1%. Find the delay difference between the slowest and fastest modes at the fiber output.
a) 0.173 μsec
b) 0.152 μsec
c) 0.96 μsec
d) 0.121 μsec

5. A multimode step-index fiber has a core refractive index of 1.5 and relative refractive index difference of 1%. The length of the optical link is 6 km. Estimate the RMS pulse broadening due to intermodal dispersion on the link.
a) 92.6 ns
b) 86.7 ns
c) 69.3 ns
d) 68.32 ns

6. The differential attenuation of modes reduces intermodal pulse broadening on a multimode optical link.
a) True
b) False

7. The index profile of a core of multimode graded index fiber is given by?
a) N (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
b) N (r) = n1 [3 – 2Δ(r2/a)2]1/2; r<a
c) N (r) = n1 [5 – 2Δ(r2/a)2]1/2; r>a
d) N (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a
Answer: d) N (r) = n1 [1 – 2Δ(r2/a)2]1/2; r<a

8. Intermodal dispersion in multimode fibers is minimized with the use of step-index fibers.
a) True
b) False

9. Estimate RMS pulse broadening per km due to intermodal dispersion for multimode step index fiber where length of fiber is 4 km and pulse broadening per km is 80.6 ns.
a) 18.23ns/km
b) 20.15ns/km
c) 26.93ns/km
d) 10.23ns/km

10. Practical pulse broadening value for graded index fiber lies in the range of __________
a) 0.9 to 1.2 ns/km
b) 0.2 to 1 ns/km
c) 0.23 to 5 ns/km
d) 0.45 to 8 ns/km
Answer: b) 0.2 to 1 ns/km

11. The modal noise occurs when uncorrected source frequency is?
a) δf>>1/δT
b) δf=1/δT
c) δf<<1/δT
d) Negligible

12. Disturbance along the fiber such as vibrations, discontinuities, connectors, splices, source/detectors coupling result in __________
a) Modal noise
b) Inter-symbol interference
c) Infrared interference

13. The modal noise can be reduced by __________
a) Decreasing width of signal longitudinal mode
b) Increasing coherence time
c) Decreasing number of longitudinal modes
d) Using fiber with large numerical aperture
Answer: d) Using fiber with large numerical aperture

14. Digital transmission is more likely to be affected by modal noise.
a) True
b) False

1. A multimode step index fiber has source of RMS spectral width of 60nm and dispersion parameter for fiber is 150psnm-1km-1. Estimate rms pulse broadening due to material dispersion.
a) 12.5ns km-1
b) 9.6ns km-1
c) 9.0ns km-1
d) 10.2ns km-1

2. A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening.
a) 30.46ns/km
b) 31.23ns/km
c) 28.12ns/km
d) 26.10ns/km

3. Γg = dβ / C*dk. What is β in the given equation?
a) Attenuation constant
b) Propagation constant
c) Boltzmann’s constant
d) Free-space

4. Most of the power in an optical fiber is transmitted in fiber cladding.
a) True
b) False

5. A single mode fiber has a zero dispersion wavelength of 1.21μm and a dispersion slope of 0.08 psnm-2km-1. What is the total first order dispersion at wavelength 1.26μm.
a) -2.8psnm-1 km-1
b) -3.76psnm-1 km-1
c) -1.2psnm-1 km-1
d) 2.4psnm-1 km-1

6. The dispersion due to material, waveguide and profile are -2.8nm-1km-1, 20.1nm-1km-1 and 23.2nm-1km-1respectively. Find the total first order dispersion?
a) 36.2psnm-1 km-1
b) 38.12psnm-1 km-1
c) 40.5psnm-1 km-1
d) 20.9psnm-1 km-1

7. Dispersion-shifted single mode fibers are created by __________
a) Increasing fiber core diameter and decreasing fractional index difference
b) Decreasing fiber core diameter and decreasing fractional index difference
c) Decreasing fiber core diameter and increasing fractional index difference
d) Increasing fiber core diameter and increasing fractional index difference
Answer:c) Decreasing fiber core diameter and increasing fractional index difference

8. An alternative modification of the dispersion characteristics of single mode fibers involves achievement of low dispersion gap over the low-loss wavelength region between __________
a) 0.2 and 0.9μm
b) 0.1 and 0.2μm
c) 1.3 and 1.6μm
d) 2 and 3μm

9. The fibers which relax the spectral requirements for optical sources and allow flexible wavelength division multiplying are known as __________
a) Dispersion-flattened single mode fiber
b) Dispersion-enhanced single mode fiber
c) Dispersion-compressed single mode fiber
d) Dispersion-standardized single mode fiber
Answer: a) Dispersion-flattened single mode fiber

10. For suitable power confinement of fundamental mode, the normalized frequency v should be maintained in the range 1.5 to 2.4μm and the fractional index difference must be linearly increased as a square function while the core diameter is linearly reduced to keep v constant. This confinement is achieved by?
a) Increasing level of silica doping in fiber core
b) Increasing level of germanium doping in fiber core
c) Decreasing level of silica germanium in fiber core
d) Decreasing level of silica doping in fiber core
Answer: b) Increasing level of germanium doping in fiber core

11. Any amount of stress occurring at the core-cladding interface would be reduced by grading the material composition.
a) True
b) False

12. The variant of non-zero-dispersion-shifted fiber is called as __________
a) Dispersion flattened fiber
b) Zero-dispersion fiber
c) Positive-dispersion fiber
d) Negative-dispersion fiber
Answer: d) Negative-dispersion fiberd) Negative-dispersion fiber

13. Non-zero-dispersion-shifted fiber was introduced in the year 2000.
a) True
b) False

1. For many applications that involve optical fiber transmission, an intensity modulation optical source is not required.
a) True
b) False

2. The optical source used for detection of optical signal is ____________
a) IR sensors
b) Photodiodes
c) Zener diodes
d) Transistors

3. An optical fiber behaves as a birefringence medium due to differences in ___________
a) Effective R-I and core geometry
c) Transmission/propagation time of waves
d) Refractive indices of glass and silica
Answer: a) Effective R-I and core geometry

4. The beat length in a single mode optical fiber is 8 cm when light from a laser with a peak wavelength 0.6μm is launched into it. Estimate the modal birefringence.
a) 1×10-5
b) 3.5×10-5
c) 2×10-5
d) 4×10-5

5. Beat length of a single mode optical fiber is 0.6cm. Calculate the difference between propagation constants for the orthogonal modes.
a) 69.8
b) 99.86
c) 73.2
d) 104.66

6. A polarization maintaining fiber operates at a wavelength 1.2μm and have a modal birefringence of 1.8*10-3. Calculate the period of perturbation.
a) 0.7 seconds
b) 0.6 seconds
c) 0.23 seconds
d) 0.5 seconds

7. When two components are equally excited at the fiber input, then for polarization maintaining fibers δΓg should be around ___________
a) 1.5ns/km
b) 1 ns/km
c) 1.2ns/km
d) 2ns/km

8. Polarization modal noise can _________ the performance of communication system.
b) Improve
c) Reduce
d) Attenuate

1. The nonlinear effects in optical fibers are large.
a) True
b) False

2. How many categories of nonlinear effects are seen in optical fibers?
a) One
b) Two
c) Three
d) Four

3. Which of the following is not related to Kerr effects?
a) Self-phase modulation
b) Cross-phase modulation
c) Four-wave mixing
d) Stimulated Raman Scattering

4. Linear scattering effects are _______ in nature.
a) Elastic
b) Non-Elastic
c) Mechanical
d) Electrical

5. Which thing is more dominant in making a fiber function as a bidirectional optical amplifier?
a) Core material
b) Pump source
d) Diameter of fiber

6. _________ semiconductor laser sources generally have broader bandwidths.
a) Injection
b) Pulsed
c) Solid-state
d) Silicon hybrid

7. Nonlinear effects which are defined by the intensity – dependent refractive index of the fiber are called as ________
a) Scattering effects
b) Kerr effects
c) Raman effects
d) Tomlinson effects

8. Self-phase modulation causes modifications to the pulse spectrum.
a) True
b) False

9. Self-phase modulation can be used for _____________
a) Enhancing the core diameter
b) Wavelength shifting
c) Decreasing the attenuation
d) Reducing the losses in the fiber

10. The beating between light at different frequencies or wavelengths in multichannel fiber transmission causes ________
a) Attenuation
b) Amplitude modulation of channels
c) Phase modulation of channels
d) Loss in transmission
Answer : c) Phase modulation of channels

11. What is different in case of cross-phase modulation from self-phase modulation?
a) Overlapping but same pulses
b) Overlapping but distinguishable pulses
c) Non-overlapping and same pulses
d) Non-overlapping but distinguishable pulses
Answer: b) Overlapping but distinguishable pulses

12. When three wave components co-propagate at angular frequency w1, w2, w3, then a new wave is generated at frequency w4, which is given by?
a) w4 = w1 – w2 – w3
b) w4 = w1 + w2 + w3
c) w4 = w1 + w2 – w3
d) w4 = w1 – w2 + w3
Answer: c) w4 = w1 + w2 – w3

13. _____________ results from a case of nonlinear dispersion compensation in which the nonlinear dispersion compensation in which the nonlinear chirp caused by self-phase modulation balances, postpones, the temporal broadening induced by group velocity delay.
a) Four wave mixing
b) Phase modulation
c) Soliton propagation
d) Raman scattering

1. What is a fundamental necessity in the fabrication of fibers for light transmission?
a) Same refractive index for both core and cladding
b) Pump source
c) Material composition of fiber
d) Variation of refractive index inside the optical fiber
Answer: d) Variation of refractive index inside the optical fiber

2. Which materials are unsuitable for the fabrication of graded index fiber?
a) Glass-like-materials
b) Mono-crystalline structures
c) Amorphous material
d) Silica based material

3. How many different categories are available for the methods of preparing optical glasses?
a) 1
b) 2
c) 3
d) 4

4. What is the first stage in liquid-phase-technique?
a) Preparation of ultra-pure material powders
b) Melting of materials
c) Decomposition
d) Crystallization
Answer: a) Preparation of ultra-pure material powders

5. Which processes are involved in the purification stage in liquid-phase-technique?
a) Filtration, Co-precipitation, Re-crystallization
b) Decomposition, Filtration, Drying
c) Doping, Drying, Decomposition
d) Filtration, Drying, Doping

6. At what temperature range, does the melting of multi components glass systems takes place?
a) 100-300 degree Celsius
b) 600-800 degree Celsius
c) 900-1300 degree Celsius
d) 1500-1800 degree Celsius

7. Fiber drawing using preform was useful for the production of graded index fibers.
a) True
b) False

8. The minute perturbations and impurities in the fiber drawing process using preform technique can result in very high losses of _____________
a) Between 500 and 1000 dB/km
b) Between 100 and 300 dB/km
c) Between 1200 and 1600 dB/km
d) More than 2000 dB/km
Answer : a) Between 500 and 1000 dB/km

9. The liquid-phase melting technique is used for the production of fibers ___________
a) With a core diameter of 50μm
b) With a core diameter less than 100μm
c) With a core diameter more than 200μm
d) With a core diameter of 100μm
Answer: c) With a core diameter more than 200μm

10. Graded index fibers produced by liquid-phase melting techniques are less dispersive than step-index fibers.
a) True
b) False

1. Which of the following is not a technique for fabrication of glass fibers?
a) Vapor phase oxidation method
b) Direct melt method
c) Lave ring method
d) Chemical vapor deposition technique

2. _____________ technique is method of preparing extremely pure optical glasses.
a) Liquid phase (melting)
c) Optical attenuation
d) Vapor Phase Deposition (VPD)
Answer: d) Vapor Phase Deposition (VPD)

3. Which of the following materials is not used as a starting material in vapor-phase deposition technique?
a) SiCl4
b) GeCl4
c) O2
d) B2O3

4. P2O5 is used as a _____________
a) Dopant
b) Starting material
d) Core glass

5. How many types of vapor-phase deposition techniques are present?
a) One
b) Two
c) Three
d) Four

6. ___________ uses flame hydrolysis stems from work on soot processes which were used to prepare the fiber with losses below 20 dB/km.

a) Outside vapor phase oxidation
b) Chemical vapor deposition
c) Liquid phase melting
d) Crystallization
Answer: a) Outside vapor phase oxidation

7. Complete the given reaction.

SiCl4 + 2H2O → SiO2 + ______

a) 2HCl
b) 4HCl
c) 2Cl2
d) 4Cl2

8. In modified chemical vapor deposition, vapor phase reactant such as _________ pass through a hot zone.
a) Halide and oxygen
b) Halide and hydrogen
c) Halide and silica
d) Hydroxides and oxygen

9. _________ is the stimulation of oxide formation by means of non-isothermal plasma maintained at low pressure in a microwave cavity surrounding the tube.
a) Outside Vapor Phase Oxidation (OVPO)
c) Modified Chemical Vapor Deposition (MCVD)
d) Plasma-activated Chemical Vapor Deposition (PCVD)
Answer: d) Plasma-activated Chemical Vapor Deposition (PCVD)

10. Only graded index fibers are made with the help of vapor-phase deposition techniques.
a) True
b) False

11. Modified Chemical Vapor Deposition (MCVD) process is also called as an inside vapor phase oxidation (IVPD) technique.
a) True
b) False

1. Multimode step index fiber has ___________
a) Large core diameter & large numerical aperture
b) Large core diameter and small numerical aperture
c) Small core diameter and large numerical aperture
d) Small core diameter & small numerical aperture
Answer: a) Large core diameter & large numerical aperture

2. A typically structured glass multimode step index fiber shows as variation of attenuation in range of ___________
a) 1.2 to 90 dB km-1 at wavelength 0.69μm
b) 3.2 to 30 dB km-1 at wavelength 0.59μm
c) 2.6 to 50 dB km-1 at wavelength 0.85μm
d) 1.6 to 60 dB km-1 at wavelength 0.90μm
Answer: c) 2.6 to 50 dB km-1 at wavelength 0.85μm

3. Multimode step index fiber has a large core diameter of range is ___________
a) 100 to 300 μm
b) 100 to 300 nm
c) 200 to 500 μm
d) 200 to 500 nm
Answer: a) 100 to 300 μm

4. Multimode step index fibers have a bandwidth of ___________
a) 2 to 30 MHz km
b) 6 to 50 MHz km
c) 10 to 40 MHz km
d) 8 to 40 MHz km
Answer: b) 6 to 50 MHz km

5. Multimode graded index fibers are manufactured from materials with ___________
a) Lower purity
b) Higher purity than multimode step index fibers.
c) No impurity
d) Impurity as same as multimode step index fibers.
Answer: b) Higher purity than multimode step index fibers.

6. The performance characteristics of multimode graded index fibers are ___________

a) Better than multimode step index fibers
b) Same as multimode step index fibers
c) Lesser than multimode step index fibers
d) Negligible
Answer:  a) Better than multimode step index fibers

7. Multimode graded index fibers have overall buffer jackets same as multimode step index fibers but have core diameters ___________
a) Larger than multimode step index fibers
b) Smaller than multimode step index fibers
c) Same as that of multimode step index fibers
d) Smaller than single mode step index fibers
Answer:  b) Smaller than multimode step index fibers

8. Multimode graded index fibers with wavelength of 0.85μm have numerical aperture of 0.29 have core/cladding diameter of ___________
a) 62.5 μm/125 μm
b) 100 μm/140 μm
c) 85 μm/125 μm
d) 50 μm/125μm

9. Multimode graded index fibers use incoherent source only.
a) True
b) False

10. In single mode fibers, which is the most beneficial index profile?
a) Step index
d) Coaxial cable

11. The fibers mostly not used nowadays for optical fiber communication system are ___________
a) Single mode fibers
b) Multimode step fibers
c) Coaxial cables

12. Single mode fibers allow single mode propagation; the cladding diameter must be at least ___________
a) Twice the core diameter
b) Thrice the core diameter
c) Five times the core diameter
d) Ten times the core diameter
Answer :d) Ten times the core diameter

13. A fiber which is referred as non-dispersive shifted fiber is?
a) Coaxial cables
b) Standard single mode fibers
c) Standard multimode fibers
d) Non zero dispersion shifted fibers
Answer :b) Standard single mode fibers

14. Standard single mode fibers (SSMF) are utilized mainly for operation in ___________
a) C-band
b) L-band
c) O-band
d) C-band and L-band

15. Fiber mostly suited in single-wavelength transmission in O-band is?
a) Low-water-peak non dispersion-shifted fibers
b) Standard single mode fibers
c) Low minimized fibers
d) Non-zero-dispersion-shifted fibers
Answer: b) Standard single mode fibers

1. When optical fibers are to be installed in a working environment, the most important parameter to be considered is?
a) Transmission property of the fiber
b) Mechanical property of the fiber
c) Core cladding ratio of the fiber
d) Numerical aperture of the fiber
Answer: b) Mechanical property of the fiber

2. It is not important to cover these optical fibers required for transmission.
a) True
b) False

3. Optical fibers for communication use are mostly fabricated from ___________
a) Plastic
b) Silica or multicomponent glass
c) Ceramics
d) Copper
Answer: b) Silica or multicomponent glass

4. An Si-O bond with a Young’s modulus of 9*1010Nm-1 have an elliptical crack of depth 7nm. The surface energy is 2.29 J. Estimate fracture stress for silica fiber.
a) 4.32*109Nm-1
b) 6.32*109Nm-1
c) 5.2*109Nm-1
d) 3*109Nm-1

5. Calculate percentage strain at break for a Si-O bond with a fracture strength of 3.52*1010Nm-1 and Young’s modulus of 9 *109Nm-1.
a) 3.1 %
b) 2.8 %
c) 4.5 %
d) 3.9 %

6. Stress corrosion must be considered while designing and testing optical fiber cables.
a) True
b) False

7. Which statistics are used for calculations of strengths of optical fibers?
a) Edwin statistics
b) Newton statistics
c) Wei-bull statistics
d) Gamma statistics

8. What does n denotes in the equation given below, if vc is the crack velocity; A is the constant for the fiber material and KI is the strength intensity factor?

vc = AKIn

a) Refractive index
b) Stress corrosion susceptibility
c) Strain
d) Young’s modulus

1. ____________ results from small lateral forces exerted on the fiber during the cabling process.
a) Attenuation
b) Micro-bending
c) Dispersion
d) Stimulated Emission

2. Microscopic meandering of the fiber core axis that is micro-bending is caused due to ___________
a) Environmental effects
b) Rough edges of the fiber
c) Large diameter of core
d) Polarization

3. How many forms of modal power distribution are considered?
a) One
b) Two
c) Three
d) Four

4. What does micro-bending losses depend on _____________
a) Core material
b) Refractive index
c) Diameter
d) Mode and wavelength

5. The fiber should be________________ to avoid deterioration of the optical transmission characteristics resulting from mode-coupling-induced micro-bending.
a) Free from irregular external pressure
b) Coupled with plastic
c) Large in diameter
d) Smooth and in a steady state
Answer: a) Free from irregular external pressure

6. The diffusion of hydrogen into optical fiber affects the ______________
a) Transmission of optical light in the fiber
b) Spectral attenuation characteristics of the fiber
c) Core of the fiber
Answer: b) Spectral attenuation characteristics of the fiber

7. __________ can induce a considerable amount of attenuation in optical fibers.
a) Micro-bending
b) Dispersion
c) Diffusion of hydrogen

8. The radiation-induced attenuation can be reduced through photo-bleaching.
a) True
b) False

9. The losses due to hydrogen absorption and reaction with fiber deposits can be temporary.
a) True
b) False

10. The losses caused due to hydrogen absorption mechanisms are in the range of ___________
a) 20 dB/km to 25 dB/km
b) 10 dB/km to 15 dB/km
c) 25 dB/km to 50 dB/km
d) 0 dB/km to 5 dB/km
Answer: c) 25 dB/km to 50 dB/km

1. The cable must be designed such that the strain on the fiber in the cable does not exceed __________
a) 0.002%
b) 0.01%
c) 0.2%
d) 0.160%

2. How many categories exists in case of cable design?
a) Two
b) Three
c) One
d) Four

3. How many types of buffer jackets are used in fiber buffering?
a) Three
b) One
c) Two
d) Four

4. Loose tube buffer jackets exhibits a low resistance to movement of the fiber.
a) True
b) False

5. An inclusion of one or more structural members in an optical fiber so as to serve as a cable core foundation around which the buffer fibers may be wrapped is called _____________
a) Attenuation
b) Splicing
c) Buffering
d) Stranding

6. Which of the following is not a strength member used in optical cable?

a) Steel wire
b) Germanium
c) Aramid yarns
d) Glass elements

7. When the stranding approach consists of individual elements (e.g. single-fiber or multi fiber loose tube buffer) than the cable is termed as _____________
a) Optical unit cable
b) Coaxial cable
c) Layer cable
d) Bare glass cable

8. The primary function of the structural member is load bearing.
a) True
b) False

9. What is the Young’s modulus of Kevlar, an aromatic polyester?
a) 9 ×1010Nm-2
b) 10 ×1010Nm-2
c) 12 ×1010Nm-2
d) 13 ×1010Nm-2

10. The cable is normally covered with an outer plastic sheath to reduce _______________
a) Abrasion
b) Armor
c) Friction
d) Dispersion

1. A measure of amount of optical fiber emitted from source that can be coupled into a fiber is termed as ______________
b) Angular power distribution
c) Coupling efficiency
d) Power-launching

2. The ratio r = (n1 – n)/(n1 – n) indicates ____________
a) Fresnel reflection
b) Reflection coefficient
c) Refraction coefficient
d) Angular power distribution coefficient

3. A GaAs optical source having a refractive index of 3.2 is coupled to a silica fiber having a refractive index of 1.42. Determine Fresnel reflection at interface in terms of percentage.
a) 13.4%
b) 17.4%
c) 17.6%
d) 14.8%

4. A particular GaAs fiber has a Fresnel reflection magnitude of 17.6% i.e. 0.176. Find the power loss between the source and the fiber?
a) 0.86 dB
b) 0.78 dB
c) 0.84 dB
d) 0.83 dB

5. Two joined step index fibers are perfectly aligned. What is the coupling loss of numerical aperture are NAR= 0.26 for emitting fiber?
a) -0.828 dB
b) -0.010 dB
c) -0.32 dB
d) 0.32 dB

6. Two joined graded index fibers that are perfectly aligned have refractive indices αR = 1.93 for receiving fiber αE = 2.15 for emitting fiber. Calculate the coupling loss.
a) 0.23 dB
b) 0.16 dB
c) 0.82 dB
d) 0.76 dB

7. How many types of misalignments occur when joining compatible fiber?
a) One
b) Two
c) Five
d) Three

8. Losses caused by factors such as core-cladding diameter, numerical aperture, relative refractive index differences, different refractive index profiles, fiber faults are known as ____________
a) Intrinsic joint losses
b) Extrinsic losses
c) Insertion losses
d) Coupling losses

9. A step index fiber has a coupling efficiency of 0.906 with uniform illumination of all propagation modes. Find the insertion loss due to lateral misalignment?
a) 0.95 dB
b) 0.40 dB
c) 0.42 dB
d) 0.62 dB

10. A graded index fiber has a parabolic refractive index profile (α=2) and core diameter of 42μm. Estimate an insertion loss due to a 2 μm lateral misalignment when there is index matching and assuming there is uniform illumination of all guided modes only.
a) 0.180
b) 0.106
c) 0.280
d) 0.080

11. Determine coupling efficiency if the misalignment loss in a graded index fiber is 0.102.
a) 0.136
b) 0.898
c) 0.982
d) 0.684

12. In a single mode fiber, the losses due to lateral offset and angular misalignment are given by 0.20 dB and 0.46 dB respectively. Find the total insertion loss.
a) 0.66 dB
b) 0.26 dB
c) 0.38 dB
d) 0.40 dB

13. The intrinsic loss through a multimode fiber joint is independent of direction of propagation.
a) True
b) False

1. A permanent joint formed between two different optical fibers in the field is known as a ____________
a) Fiber splice
b) Fiber connector
c) Fiber attenuator
d) Fiber dispersion

2. How many types of fiber splices are available?
a) One
b) Two
c) Three
d) Four

3. The insertion losses of the fiber splices are much less than the Fresnel reflection loss at a butted fiber joint.
a) True
b) False

4. What is the main requirement with the fibers that are intended for splicing?
a) Smooth and oval end faces
b) Smooth and square end faces
c) Rough edge faces
d) Large core diameter
Answer: b) Smooth and square end faces

5. In score and break process, which of the following is not used as a cutting tool?
a) Diamond
b) Sapphire
c) Tungsten carbide
d) Copper

6. The heating of the two prepared fiber ends to their fusing point with the application of required axial pressure between the two optical fibers is called as ____________
a) Mechanical splicing
b) Fusion splicing
c) Melting
d) Diffusion

7. Which of the following is not used as a flame heating source in fusion splicing?
a) Microprocessor torches
b) Ox hydric burners
c) Electric arc
d) Gas burner

8. The rounding of the fiber ends with a low energy discharge before pressing the fibers together and fusing with a stronger arc is called as ____________
a) Pre-fusion
b) Diffusion
c) Crystallization
d) Alignment

9. _____________ is caused by surface tension effects between the two fiber ends during fusing.
a) Pre-fusion
b) Diffusion
c) Self-alignment
d) Splicing

10. Average insertion losses as low as _________ have been obtained with multimode graded index and single-mode fibers using ceramic capillaries.
a) 0.1 dB
b) 0.5 dB
c) 0.02 dB
d) 0.3 dB

11. _____________ are formed by sandwiching the butted fiber ends between a V-groove glass substrate and a flat glass retainer plate.
a) Springroove splices
b) V-groove splices
c) Elastic splices
d) Fusion splices

12. Mean splice insertion losses of 0.05 dB are obtained using multimode graded index fibers with the Springroove splice.
a) True
b) False

13. Alignment accuracy of the order ___________ is obtained using the three glass rod alignment sleeve.
a) 0.23 μm
b) 0.15 μm
c) 0.05 μm
d) 0.01 μm

14. In case of multiple fusion, splice losses using an electric arc fusion device with multimode graded index fiber range from ____________
a) 0.01 to 0.04 dB
b) 0.19 to 0.25 dB
c) 0.12 to 0.15 dB
d) 0.04 to 0.12 dB
Answer: d) 0.04 to 0.12 dB

1. Demountable fiber connectors are more difficult to achieve than optical fiber splices.
a) True
b) False

2. What is the use of an index-matching material in the connector between the two jointed fibers?
a) To decrease the light transmission through the connection
b) To increase the light transmission through the connection
c) To induce losses in the fiber
d) To make a fiber dispersive
Answer:  b) To increase the light transmission through the connection

3. How many categories of fiber connectors exist?
a) One
b) Three
c) Two
d) Four

4. The basic ferrule connector is also called as _____________
a) Groove connector
b) Beam connector
c) Multimode connector
d) Concentric sleeve connector

5. What is the use of watch jewel in cylindrical ferrule connector?

a) To obtain the diameter and tolerance requirements of the ferrule
b) For polishing purposes
c) Cleaving the fiber
d) To disperse a fiber
Answer: a) To obtain the diameter and tolerance requirements of the ferrule

6. The concentricity errors between the fiber core and the outside diameter of the jeweled ferrule are in the range of ___________ with multimode step-index fibers.
a) 1 to 3μm
b) 2 to 6μm
c) 7 to 10μm
d) 12 to 20μm

7. The typical average losses for multimode graded index fiber and single mode fiber with the precision ceramic ferrule connector are _____________ respectively.
a) 0.3 and 0.5 dB
b) 0.2 and 0.3 dB
c) 0.1 and 0.2 dB
d) 0.4 and 0.7 dB
Answer: b) 0.2 and 0.3 dB

8. Bi-conical ferrule connectors are less advantageous than cylindrical ferrule connectors.
a) FalseStat
b) True

9. In connectors, the fiber ends are separated by some gap. This gap ranges from ____________
a) 0.040 to 0.045 mm
b) 0.025 to 0.10 mm
c) 0.12 to 0.16 mm
d) 0.030 to 0.2mm
Answer: b) 0.025 to 0.10 mm

1. What is the use of interposed optics in expanded beam connectors?
a) To achieve lateral alignment less critical than a butt-joined fiber connector
b) To make a fiber loss free
c) To make a fiber dispersive
d) For index-matching
Answer:  a) To achieve lateral alignment less critical than a butt-joined fiber connector

2. The expanded beam connectors use ____________ for beam expansion and reduction.
a) Square micro-lens
b) Oval micro-lens
c) Spherical micro-lens
d) Rectangular micro-lens

3. Lens-coupled expanded beam connectors exhibit average losses of _________ in case of single mode and graded index fibers.
a) 0.3 dB
b) 0.7 dB
c) 0.2 dB
d) 1.5 dB

4. Sapphire ball lens expanded beam design is successful than spherical lens coupled design.
a) True
b) False

5. The fiber is positioned at the ________ of the lens in order to obtain a collimated beam and to minimize lens-to-lens longitudinal misalignment effects.
a) Aperture
b) Focal length
c) Curve
d) Exterior circumference

6. ___________ exhibits a parabolic refractive index profile with a maximum at the axis similar to graded index fiber.
a) Lens coupled design
b) Sapphire ball lens
c) Spherical micro-lens
d) GRIN-rod lens

7. The GRIN-rod lens can produce a collimated output beam with a divergent angle αof between _____________ from a light source situated on, or near to, the opposite lens face.
a) 1 to 5 degrees
b) 9 to 16 degrees
c) 4 to 8 degrees
d) 25 to 50 degrees
Answer:  a) 1 to 5 degrees

8. In the given equation, if r is the radial distance, n is the refractive index; what does z stands for?

dr2/dz2 = (1/n) (d n/dr)

a) Focal length
b) Distance along the optical axis
c) Axial angle
d) Diameter
Answer:  b) Distance along the optical axis

9. The majority of the GRIN-rod lenses have diameters in the range of ____________
a) 2 to 2.5 mm
b) 3 to 4 mm
c) 0.1 to 0.4 mm
d) 0.5 to 2 mm
Answer:  d) 0.5 to 2 mm

10. Which of the following factors does not cause divergence of the collimated beam from a GRIN-rod lens?
a) Lens cut length
b) Size of fiber core
c) Refractive index profile
d) Chromatic aberration

11. GRIN-rod lens connectors have loss characteristics that are independent of the modal power distribution in the fiber.
a) True
b) False

1. When considering source-to-fiber coupling efficiencies, the ________ is an important parameter than total output power.
a) Numerical aperture
b) Radiance of an optical source
c) Coupling efficiency
d) Angular power distribution

2. It is a device that distributes light from a main fiber into one or more branch fibers.
a) Optical fiber coupler
b) Optical fiber splice
c) Optical fiber connector
d) Optical isolator

3. Optical fiber couplers are also called as ________________
a) Isolators
b) Circulators
c) Directional couplers
d) Attenuators

4. How many types of multiport optical fiber couplers are available at present?
a) Two
b) One
c) Four
d) Three

5. The optical power coupled from one fiber to another is limited by ____________
a) Numerical apertures of fibers
b) Varying refractive index of fibers
c) Angular power distribution at source
d) Number of modes propagating in each fiber
Answer:d) Number of modes propagating in each fiber

6. ________ couplers combine the different wavelength optical signal onto the fiber or separate the different wavelength optical signal output from the fiber.

a) 3-port
b) 2*2-star
c) WDM
d) Directional

7. How many fabrication techniques are used for 3 port fiber couplers?
a) One
b) Two
c) Three
d) Four

8. Which is the most common method for manufacturing couplers?
a) Wavelength division multiplexing
b) Lateral offset method
c) Semitransparent mirror method
d) Fused bi-conical taper (FBT) technique
Answer:d) Fused bi-conical taper (FBT) technique

9. Couplers insertion loss is same as that of excess loss.
a) True
b) False

10. A four-port multimode fiber FBT coupler has 50 μW optical power launched into port 1. The measured output power at ports 2,3 and 4 are 0.003, 23.0 and 24.5 μW respectively. Determine the excess loss.
a) 0.22 dB
b) 0.33 dB
c) 0.45 dB
d) 0.12 dB

11. A four-port FBT coupler has 60μW optical power launched into port one. The output powers at ports 2, 3, 4 are 0.0025, 18, and 22 μW respectively. Find the split ratio?
a) 42%
b) 46%
c) 52%
d) 45%

12. How many manufacturing methods are used for producing multimode fiber star couplers?
a) Two
b) One
c) Three
d) Five

13. Calculate the splitting loss if a 30×30 port multimode fiber star coupler has 1 mW of optical power launched into an input port.
a) 13 dB
b) 15 dB
c) 14.77 dB
d) 16.02 dB

14. A _____________ coupler comprises a number of cascaded stages, each incorporating three or four-port FBT couplers to obtain a multiport output.
a) Star
c) WDM
d) Three-port

15. A number of three-port single-mode fiber couplers are used in the fabrication of a ladder coupler with 16 output ports. The three-port couplers each have an excess loss of 0.2 dB along with a splice loss of 0.1 dB at the interconnection of each stage. Determine the excess loss.
a) 1.9 dB
b) 1.4 dB
c) 0.9 dB
d) 1.1 dB

1. An FBG is developed within a fiber core having a refractive index of 1.30. Find the grating period for it to reflect an optical signal with a wavelength of 1.33μm.
a) 0.51 μm
b) 0.58 μm
c) 0.61 μm
d) 0.49 μm

2. It is a passive device which allows the flow of optical signal power in only one direction and preventing reflections in the backward direction.
a) Fiber slice
b) Optical fiber connector
c) Optical isolator
d) Optical coupler

3. Which feature of an optical isolator makes it attractive to use with optical amplifier?
a) Low loss
b) Wavelength blocking
c) Low refractive index
d) Attenuation

4. Magneto-optic devices can be used to function as isolators.
a) True
b) False

5. How many implementation methods are available for optical isolators?

a) One
b) Four
c) Two
d) Three

6. A device which is made of isolators and follows a closed loop path is called as a ____________
a) Circulator
b) Gyrator
c) Attenuator
d) Connector

7. The commercially available circulators exhibit insertion losses around ________________
a) 2 dB
b) 0.7 dB
c) 0.2 dB
d) 1 dB

8. A combination of a FBG and optical isolators can be used to produce non-blocking optical wavelength division add/draw multiplexers.
a) True
b) False

1. A device which converts electrical energy in the form of a current into optical energy is called as ___________
a) Optical source
b) Optical coupler
c) Optical isolator
d) Circulator

2. How many types of sources of optical light are available?
a) One
b) Two
c) Three
d) Four

3. The frequency of the absorbed or emitted radiation is related to difference in energy E between the higher energy state E2 and the lower energy state E1. State what h stands for in the given equation?

E = E2 - E1 = hf

a) Gravitation constant
b) Planck’s constant
c) Permittivity
d) Attenuation constant

4. The radiation emission process (emission of a proton at frequency) can occur in __________ ways.
a) Two
b) Three
c) Four
d) One

5. Which process gives the laser its special properties as an optical source?

a) Dispersion
b) Stimulated absorption
c) Spontaneous emission
d) Stimulated emission

6. An incandescent lamp is operating at a temperature of 1000K at an operating frequency of 5.2×1014 Hz. Calculate the ratio of stimulated emission rate to spontaneous emission rate.
a) 3×10-13
b) 1.47×10-11
c) 2×10-12
d) 1.5×10-13

7. The lower energy level contains more atoms than upper level under the conditions of ________________
a) Isothermal packaging
b) Population inversion
c) Thermal equilibrium
d) Pumping

8. __________________ in the laser occurs when photon colliding with an excited atom causes the stimulated emission of a second photon.
a) Light amplification
b) Attenuation
c) Dispersion
d) Population inversion

9. A ruby laser has a crystal of length 3 cm with a refractive index of 1.60, wavelength 0.43 μm. Determine the number of longitudinal modes.
a) 1×102
b) 3×106
c) 2.9×105
d) 2.2×105

10. A semiconductor laser crystal of length 5 cm, refractive index 1.8 is used as an optical source. Determine the frequency separation of the modes.
a) 2.8 GHz
b) 1.2 GHz
c) 1.6 GHz
d) 2 GHz

a) True
b) False

12. An injection laser has active cavity losses of 25 cm-1 and the reflectivity of each laser facet is 30%. Determine the laser gain coefficient for the cavity it has a length of 500μm.
a) 46 cm-1
b) 51 cm-1
c) 50 cm-1
d) 49.07 cm-1

13. Longitudinal modes contribute only a single spot of light to the laser output.
a) True
b) False

14. Considering the values given below, calculate the mode separation in terms of free space wavelength for a laser. (Frequency separation = 2GHz, Wavelength = 0.5 μm)
a) 1.4×10-11
b) 1.6×10-12
c) 1×10-12
d) 6×10-11

1. Stimulated emission by recombination of injected carriers is encouraged in __________
a) Semiconductor injection laser
b) Gas laser
c) Chemist laser
d) Dye laser

2. In semiconductor injection laser, narrow line bandwidth is of the order?
a) 1 nm or less
b) 4 nm
c) 5 nm
d) 3 nm
Answer: a) 1 nm or less

3. Injection laser have a high threshold current density of __________
a) 104Acm-2 and more
b) 102Acm-2
c) 10-2Acm-2
d) 10-3Acm-2

4. ηT is known as slope quantum efficiency.
a) True
b) False

5. The total efficiency of an injection laser with GaAs active region is 12%. The applied voltage is 3.6 V and band gap energy for GaAs is 2.34 eV. Determine external power efficiency.
a) 7.8 %
b) 10 %
c) 12 %
d) 6 %

6. In a DH laser, the sides of cavity are formed by _______________

a) Cutting the edges of device
b) Roughening the edges of device
c) Softening the edges of device
d) Covering the sides with ceramics
Answer: b) Roughening the edges of device

7. A particular laser structure is designed so that the active region extends the edges of devices.
a) True
b) False

8. Gain guided laser structure are __________
a) Chemical laser
b) Gas laser
c) DH injection laser
d) Quantum well laser

9. Laser modes are generally separated by few __________
a) Tenths of micrometer
b) Tenths of nanometer
c) Tenths of Pico-meter
d) Tenths of millimeter

10. The spectral width of emission from the single mode device is __________
a) Smaller than broadened transition line-width
b) Larger than broadened transition line-width
c) Equal the broadened transition line-width
d) Cannot be determined

11. Single longitudinal mode operation is obtained by __________
a) Eliminating all transverse mode
b) Eliminating all longitudinal modes
c) Increasing the length of cavity
d) Reducing the length of cavity
Answer:  d) Reducing the length of cavity

12. A correct DH structure will restrict the vertical width of waveguide region is?
a) 0.5μm.
b) 0.69 μm
c) 0.65 μm
d) Less than 0.4 μm

13. The external power efficiency of an injection laser with a GaAs is 13% having band gap energy of 1.64 eV. Determine external power efficiency.
a) 0.198
b) 0.283
c) 0.366
d) 0.467

1. In multimode injection lasers, the construction of current flow to the strip is obtained in structure by __________
a) Covering the strip with ceramic
b) Intrinsic doping
c) Implantation outside strip region with protons
d)Implantation outside strip region with electrons
Answer: c) Implantation outside strip region with protons

2. What is the strip width of injection laser?
a) 12 μm
b) 11.5 μm
c) Less than 10 μm
d) 15 μm
Answer: c) Less than 10 μm

3. Some refractive index variation is introduced into lateral structure of laser.
a) True
b) False

4. Buried hetero-junction (BH) device is a type of _____________ laser where the active volume is buried in a material of wider band-gap and lower refractive index.
a) Gas lasers.
b) Gain guided lasers.
c) Weak index guiding lasers.
d) Strong index guiding lasers.
Answer: d) Strong index guiding lasers.

5. In Buried hetero-junction (BH) lasers, the optical field is confined within __________
a) Transverse direction
b) Lateral direction
c) Outside the strip
d) Both transverse and lateral direction
Answer: d) Both transverse and lateral direction

6. A double-channel planar buried hetero-structure (DCP BH) has a planar active region, the confinement material is?

a) Alga AS
b) InGaAsP
c) GaAs
d) SiO2

7. Problems resulting from parasitic capacitances can be overcome __________
a) Through regrowth of semi-insulating material
b) By using oxide material
c) By using a planar InGaAsP active region
d) By using a AlGaAs active region
Answer: a) Through regrowth of semi-insulating material

8. Quantum well lasers are also known as __________
a) BH lasers
b) DH lasers
c) Chemical lasers
d) Gain-guided lasers

9. Quantum well lasers are providing high inherent advantage over __________
a) Chemical lasers
b) Gas lasers
c) Conventional DH devices
d) BH device

10. Strip geometry of a device or laser is important.
a) True
b) False

11. Better confinement of optical mode is obtained in __________
a) Multi Quantum well lasers
b) Single Quantum well lasers
c) Gain guided lasers
d) BH lasers
Answer: a) Multi Quantum well lasers

12. Multi-quantum devices have superior characteristics over __________
a) BH lasers
b) DH lasers
c) Gain guided lasers
d) Single-quantum-well devices

13. Dot-in-well device is also known as __________
a) DH lasers
b) BH lasers
c) QD lasers
d) Gain guided lasers

14. A BH can have anything from a single electron to several electrons.
a) True
b) False

15. QD lasers have a very low threshold current densities of range __________
a) 0.5 to 5 A cm-2
b) 2 to 10 A cm-2
c) 10 to 30 A cm-2
d) 6 to 20 A cm-2
Answer: d) 6 to 20 A cm-2

1. __________________ may be improved through the use of frequency-selective feedback so that the cavity loss is different for various longitudinal modes.
a) Frequency selectivity
b) Longitudinal mode selectivity
c) Electrical feedback
d) Dissipated power

2. Device which apply the frequency-selective feedback technique to provide single longitudinal operation are referred to as ________________
a) DSM lasers
b) Nd: YAG lasers
c) Glass fiber lasers
d) QD lasers

3. Which of the following does not provide single frequency operation?
a) Short cavity resonator
b) DSM lasers
c) Coupled cavity resonator
d) Fabry-Perot resonator

4. A method for increasing the longitudinal mode discrimination of an injection laser which is commonly used?
a) Decreasing refractive index
b) Increasing the refractive index
c) Increasing cavity length
d) Shortening of cavity length
Answer: d) Shortening of cavity length

5. Conventional cleaved mirror structures are difficult to fabricate with the cavity lengths below __________
a) 200 μm and greater than 150 μm
b) 100 μm and greater than 50 μm
c) 50 μm
d) 150 μm

6. In the given equation, corrugation period is given by lλb/2Ne. If λb is the Bragg wavelength, then what does ‘l’ stand for?
a) Length of cavity
b) Limitation index
c) Integer order of grating
d) Refractive index
Answer: c) Integer order of grating

7. The first order grating (l=1) provide the strongest coupling within the device.
a) True
b) False

8. The semiconductor lasers employing the distributed feedback mechanism are classified in _________________ categories.
a) One
b) Two
c) Three
d) Four

9. DBF-BH lasers exhibit low threshold currents in the range of ________________
a) 40 to 50 mA
b) 21 to 30 mA
c) 2 to 5 mA
d) 10 to 20 mA
Answer: d) 10 to 20 mA

10. Fabry-Perot devices with BH geometries high modulation speeds than DFB-BH lasers.
a) True
b) False

11. The InGaAsP/InP double channel planar DFB-BH laser with a quarter wavelength shifted first order grating provides a single frequency operation and incorporates a phase shift of ______________

12. The narrow line-width obtained under the CW operation for quarter wavelength shifted DFB laser is ________________
a) 2 MHz
b) 10 MHz
c) 3 MHz
d) 1 MHz

13. Line-width narrowing is achieved in DFB lasers by a strategy referred as _______________
a) Noise partition
b) Grating
c) Tuning
d) Bragg wavelength detuning

14. _________________ is a technique used to render the non-conducting material around the active cavity by producing permanent defects in the implanted area.
a) Dispersion
b) Ion de-plantation
c) Ion implantation
d) Attenuation

# Injection Laser Characteristics

1. The threshold temperature coefficient for InGaAsP devices is in the range of __________
a) 10-40 K
b) 40-75 K
c) 120-190 K
d) 150-190 K

2. The process where the energy released during the recombination of an electron-hole event getting transferred to another carrier is known as __________
a) Inter-valence bond absorption
b) Auger recombination
c) Carrier leakage effects
d) Exothermic actions

3. Auger recombination can be reduced by using __________
a) Strained MQW structure
b) Strained SQW structure
c) Gain-guided strained structure
d) Strained Quantum dots lasers

4. High strain in strained MCQ structure should be incorporated.
a) True
b) False

5. The parameter that prevents carrier from recombination is __________
a) Auger recombination
b) Inter-valence band absorption
c) Carrier leakage
d) Low temperature sensitivity

6. Determine the threshold current density for an AlGaAs injection laser with T0=180k at 30°C.

a) 6.24
b) 9.06
c) 3.08
d) 5.09

7. The phenomenon occurring when the electron and photon population within the structure comes into equilibrium is known as __________
a) Auger recombination
b) Inter-valence band absorption
c) Carrier leakage
d) Relaxation oscillations

8. When a current pulse reaches a laser having parasitic capacitance after the initial delay time, that pulse will __________
a) Have no effect
b) Will get vanished
c) Becomes narrower

9. Reducing delay time and ____________ are of high importance for lasers.
a) Auger recombination
b) Inter-valence band absorption
c) Carrier leakage effects
d) Relaxation oscillations

10. Dynamic line-width broadening under the direct modulation of injection current is known as __________
a) Auger recombination
b) Inter-valence band absorption
c) Carrier leakage effects
d) Frequency Chirping

11. A particular characteristic or parameter that occurs during analog transmission of injection lasers is?
a) Noise
b) Mode hopping
c) Carrier leakage effects
d) Frequency Chirping

12. Intensity of output from semiconductor injection lasers leading to optical intensity noise is due to __________
a) Fluctuations in amplitude
b) Mode hopping
c) Carrier leakage effects
d) Frequency Chirping

13. In multimode lasers the optical feedback from unnecessary external reflections affecting stability of frequency and intensity is?
a) Remains unaffected
c) Reduced
d) Gets totally vanished

14. Reduction in the number of modes in multimode fiber increases the mode partition noise.
a) False
b) True

15. The behavior of laser occurring when current is increased above threshold particularly is?
a) Mode hopping
b) Auger recombination
c) Frequency chirping
d) Noise

# NON- Semiconductor Lasers

1. ____________________ lasers are presently the major laser source for optical fiber communications.
a) Semiconductor
b) Non-Semiconductor
c) Injection
d) Solid-state

2. In Nd: YAG lasers, the maximum doping levels of neodymium is ____________
a) 0.5 %
b) 1.5 %
c) 1.8 %
d) 2 %

3. Which of the following is not a property of Nd: YAG laser that enables its use as an optical fiber communication source?
a) Single mode operation
b) Narrow line-width
d) Semiconductors and integrated circuits
Answer: d) Semiconductors and integrated circuits

4. The Nd: YAG laser has a narrow line-width which is ________________
a) < 0.01 nm
b) > 0.01 nm
c) > 1 mm
d) > 1.6 mm

5. The strongest pumping bands is a four level system of Nd: YAG laser at wavelength of range_________________
a) 0.25 and 0.56 nm
b) 0.75 and 0.81 nm
c) 0.12 and 0.23 nm
d) 1 and 2 nm
Answer:  b) 0.75 and 0.81 nm

6. The Nd: YAG laser is costlier than earth-doped glass fiber laser.
a) True
b) False

7. It is a resonant cavity formed by two parallel reflecting mirrors separated by a mirror separated by a medium such as air or gas is?
a) Optical cavity
b) Wheatstone’s bridge
c) Oscillator
d) Fabry-perot resonator

8. In a three level system, the threshold power decreases inversely with the length of the fiber gain medium.
a) True
b) False

9. Which of the following co-dopant is not employed by neodymium and erbium doped silica fiber lasers?
a) Phosphorus pent oxide
b) Germania
c) Nitrogen
d) Alumina

10. Dopants levels in glass fiber lasers are generally ___________
a) Low
b) High
c) Same as that of GRIN rod lens laser
d) Same as that of semiconductor laser

11. _______________ fibers include addition of lead fluoride to the core glass in order to raise the relative refractive index.
a) Solid-state
b) GaAs
c) Semiconductor
d) ZBLANP

12. The lasing output of the basic Fabry-perot cavity fiber is restricted to between ____________
a) 1 and 2 nm
b) 5 and 10 nm
c) 3 and 6 nm
Answer: b) 5 and 10 nm

13. In Fabry-perot laser, the lower threshold is obtained by ___________
a) Increasing the refractive index
b) Decreasing the refractive index
c) Reducing the slope efficiency
d) Increasing the slope efficiency
Answer: c) Reducing the slope efficiency

14. When did the non-semiconductor laser developed?
a) 1892
b) 1946
c) 1985
d) 1993

15. Y3Al5 O12 is a molecular formula for _____________
a) Ytterbium aluminate
b) Yttrium oxide
c) Ytterbium oxy-aluminate
d) Yttrium-aluminum garnet

# Tunable Lasers

1. Which of these factors are critical in affecting the system performance in the case of coherent optical fiber transmission?
a) Laser line-width and stability
b) Refractive index and index difference
d) Frequency

2. _______________ occurs as a result of the change in lasing frequency with gain.
a) Frequency multiplication
b) Dispersion
c) Attenuation

3. Laser cavity length can be extended by ___________
a) Increasing the refractive index
b) Reducing frequency
c) Introduction of external feedback
d) Using GRIN-rod lenses

4. What is the purpose of wavelength dispersive element is LEC lasers?
a) Wavelength selectivity
b) Reduction of line-width
c) Frequency multiplication
d) Avalanche multiplication

5. An effective method to reduce the line-width is to make the cavity longer.
a) True
b) False

a) Electromagnetic
b) Acousto-optic
c) Dispersive

7. How many techniques are used to tune monolithic integrated devices (lasers)?
a) Five
b) One
c) Two
d) Three

8. _________________ laser can be produced when a coupler section is introduced between the amplifier and phase sections of a structure.
a) SG-DBR
b) GCSR
c) Y 4-shifted
d) DSM

9. The rare-earth-doped fiber lasers have spectral line-width in the range of _________________
a) 0.1 to 1 nm
b) 1.2 to 1.5 nm
c) 6 to 10 nm
d) 2 to 2.3 nm

10. The lasing line-width of Fox-smith resonator is ____________________
a) Less than 1 MHz
b) 1 MHz
c) 2 MHz
d) Greater than 3 MHz

11. What is the widest tuning range obtained in optical fiber laser structure?
a) 60 nm
b) 80 nm
c) More than 100 nm
d) 100 nm

12. How many techniques can be used to increase the injection cavity length?
a) One
b) Two
c) Three
d) Four

13. The mechanism which results from a refractive index change in the passive waveguide layer is called as ___________
a) Absorption
b) Spontaneous emission
c) Monolithic inversion
d) Bragg wavelength control

14. How many sections are included in a sampling grating distributed Bragg-reflector laser (SG-DBR)?
a) Four
b) Five
c) Three
d) Two

15. Fiber based lasers provide diffraction-limited power at higher levels than solid-state laser.
a) True
b) False

# Mid Infrared and Far Infrared Lasers

1. The parameters having a major role in determining threshold current of efficiency of injection laser are ___________
a) Angle recombination and optical losses
b) Frequency chirping
c) Relaxation oscillation
d) Mode hopping
Answer:a) Angle recombination and optical losses

2. Auger current is mostly ___________________ for material with band gap providing longer wavelength emission.
a) Unaffected
b) Lesser
c) Larger
d) Vanishes

3. Injection lasers operating in smaller wavelengths are subjected to increased carrier losses.
a) True
b) False

4. Devices based on quaternary PbSnSeTe and their ternary compounds, emit at wavelength?
a) Between 3-4 μm
b) Longer than 4 μm
c) Between 3.5 to 4.2 μm
d) Between 2 to 3 μm

5. Replacing Sn with Eu, Cd or Ge in some _________________ the band gap.
a) Remove the band gap
b) Does not affect
c) Decreases
d) Increases

.6. Lasing obtained in __________ when 191 mW of pump light at a wavelength of 0.477 μm is launched into laser.
a) Ternary PbSnSeTe alloy laser
b) Quaternary PbSnSeTe alloy laser
c) Doped Fluoro-zirconate fiber
d) Ternary PbEuTe alloy laser

7. The thulium doped fiber laser when pumped with alexandrite laser output at 0.786 μm, the laser emits at ___________
a) 0.6 μm
b) 0.8 μm
c) 2.3 μm
d) 1.2μm

8. The diode-cladding-pumped Erbium praseodymium-doped fluoride device operates at wavelength.
a) Around 3 μm
b) 4 μm
c) 2.6 μm
d) 1.04 μm

9. A technique based on inter-sub band transition is known as ___________
a) Auger recombination
b) Frequency chirping
c) Inter-valence band absorption

10. In a QC laser, a same electron can emit number of photons.
a) True
b) False

11. The phenomenon resulting in the electrons to jump from one state to another each time emitting of photon is known as ___________
a) Inter-valence band absorption
b) Mode hopping
d) Quantum confinement

12. A QC laser is sometimes referred as ___________
a) Unipolar laser
b) Bipolar laser
c) Gain guided laser
d) Non semiconductor laser

13. In QC lasers, it is possible to obtain different output signal wavelengths. This can be achieved by ___________
a) Inter-valence band absorption
b) Mode hopping
d) Selecting layers of different thickness
Answer:d) Selecting layers of different thickness

14. QC lasers ______________ the performance characteristics.
a) Have negligible effects
b) Does not affects
c) Improves

a) Mode hopping
b) Auger recombination
c) Control over layers of material
d) Properties of material
Answer:c) Control over layers of material

# LED Power and Efficiency

1. The absence of _______________ in LEDs limits the internal quantum efficiency.
a) Proper semiconductor
c) Optical amplification through stimulated emission
d) Optical amplification through spontaneous emission
Answer:c) Optical amplification through stimulated emission

2. The excess density of electrons Δnand holes Δpin an LED is ____________
a) Equal
b) Δpmore than Δn
c) Δn more than Δp
d) Does not affects the LED

3. The hole concentration in extrinsic materials is _________ electron concentration.
a) much greater than
b) lesser than
c) equal to
d) negligible difference with

a) True
b) False

5. In a junction diode, an equilibrium condition occurs when ____________
a) Δngreater than Δp
b) Δnsmaller than Δp
c) Constant current flow
d) Optical amplification through stimulated emission

a) 41.17 ns
b) 35 ns
c) 40 ns
d) 37.5 ns

7. Determine the internal quantum efficiency generated within a device when it has a radiative recombination lifetime of 80 ns and total carrier recombination lifetime of 40 ns.
a) 20 %
b) 80 %
c) 30 %
d) 40 %

8. Compute power internally generated within a double-heterojunction LED if it has internal quantum efficiency of 64.5 % and drive current of 40 mA with a peak emission wavelength of 0.82 μm.
a) 0.09
b) 0.039
c) 0.04
d) 0.06

9. The Lambertian intensity distribution __________ the external power efficiency by some percent.
a) Reduces
b) Does not affects
c) Increases
d) Have a negligible effect

10. A planar LED fabricated from GaAs has a refractive index of 2.5. Compute the optical power emitted when transmission factor is 0.68.
a) 3.4 %
b) 1.23 %
c) 2.72 %
d) 3.62 %

11. A planar LED is fabricated from GaAs is having a optical power emitted is 0.018% of optical power generated internally which is 0.018% of optical power generated internally which is 0.6 P. Determine external power efficiency.
a) 0.18%
b) 0.32%
c) 0.65%
d) 0.9%

12. For a GaAs LED, the coupling efficiency is 0.05. Compute the optical loss in decibels.
a) 12.3 dB
b) 14 dB
c) 13.01 dB
d) 14.6 dB

13. In a GaAs LED, compute the loss relative to internally generated optical power in the fiber when there is small air gap between LED and fiber core. (Fiber coupled = 5.5 * 10-4Pint)
a) 34 dB
b) 32.59 dB
c) 42 dB
d) 33.1 dB

14. Determine coupling efficiency into the fiber when GaAs LED is in close proximity to fiber core having numerical aperture of 0.3.
a) 0.9
b) 0.3
c) 0.6
d) 0.12

15. If a particular optical power is coupled from an incoherent LED into a low-NA fiber, the device must exhibit very high radiance.
a) True
b) False

# LED Structures

. The amount of radiance in planer type of LED structures is ____________
a) Low
b) High
c) Zero
d) Negligible

2. In optical fiber communication _____________ major types of LED structures are used.
a) 2
b) 4
c) 6
d) 3

3. As compared to planar LED structure, Dome LEDs have ______________ External power efficiency ___________ effective emission area and _____________ radiance.
a) Greater, lesser, reduced
b) Higher, greater, reduced
c) Higher, lesser, increased
d) Greater, greater, increased

4. The techniques by Burros and Dawson in reference to homo structure device is to use an etched well in GaAs structure.
a) True
b) False

5. In surface emitter LEDs, more advantage can be obtained by using ____________
a) BH structures
b) QC structures
c) DH structures
d) Gain-guided structure

a) Cannot be determined
b) Negligible
c) High
d) Very low

7. DH surface emitter generally give ____________
a) More coupled optical power
b) Less coupled optical power
c) Low current densities
Answer: a) More coupled optical power

8. A DH surface emitter LED has an emission area diameter of 60μm. Determine emission area of source.
a) 1.534*10-6
b) 5.423*10-3
c) 3.564*10-2
d) 2.826*10-9

9. Estimate optical power coupled into fiber of DH SLED having emission area of 1.96*10-5, radiance of 40 W/rcm2, numerical aperture of 0.2 and Fresnel reflection coefficient of 0.03 at index matched fiber surface.
a) 5.459*10-5
b) 1.784*10-3
c) 3.478*102
d) 9.551*10-5

10. In a multimode fiber, much of light coupled in the fiber from an LED is ____________
a) Increased
b) Reduced
c) Lost
d) Unaffected

11. Determine the overall power conversion efficiency of lens coupled SLED having forward current of 20 mA and forward voltage of 2 V with 170 μWof optical power launched into multimode step index fiber.
a) 1.256*10-5
b) 4.417*102
c) 4.25*10-3
d) 2.14*10-3

12. The overall power conversion efficiency of electrical lens coupled LED is 0.8% and power applied 0.0375 V. Determine optical power launched into fiber.
a) 0.03
b) 0.05
c) 0.3
d) 0.01

13. Mesa structured SLEDs are used ____________

14. The InGaAsP is emitting LEDs are realized in terms of restricted are ____________
a) Length strip geometry
d) Coupled optical power

15. The active layer of E-LED is heavily doped with ____________
a) Zn
b) Eu
c) Cu
d) Sn

# LED Characteristics

1. Intrinsically _________________ are a very linear device.
a) Injection lasers
b) DH lasers
c) Gain-guided
d) LEDs

2. Linearizing circuit techniques are used for LEDs.
a) True
b) False

3. The internal quantum efficiency of LEDs decreasing _______________ with ________________ temperature.
a) Exponentially, decreasing
b) Exponentially, increasing
c) Linearly, increasing
d) Linearly, decreasing

4. To utilize _____________________ of SLDs at elevated temperatures, the use of thermoelectric coolers is important.
a) Low-internal efficiency
b) High-internal efficiency
c) High-power potential
d) Low-power potential

5. For particular materials with smaller bandgap energies operating in _____________ wavelength, the linewidth tends to ______________
a) 2.1 to 2.75 μm, increase
b) 1.1 to 1.7 μm, increase
c) 2.1 to 3.6 μm, decrease
d) 3.5 to 6 μm, decrease
Answer:b) 1.1 to 1.7 μm, increase

6. The active layer composition must be adjusted if a particular center wavelength is desired.
a) True
b) False

7. In optical fiber communication, the electrical signal dropping to half its constant value due to modulated portion of optical signal corresponds to _______
a) 6 dB
b) 3 dB
c) 4 dB
d) 5 dB

8. The optical 3 dB point occurs when currents ratio is equal to _____________
a) 8 /3
b) 2/2
c) 1/2
d) 3/4

9. The optical bandwidth is _____________ the electrical bandwidth.
a) Smaller
b) Greater
c) Same as
d) Zero with respect to

10. When a constant d.c. drive current is applied to device, the optical o/p power is 320 μm. Determine optical o/p power when device is modulated at frequency 30 MHz with minority carrier recombination lifetime of LED i.e. 5ns.
a) 4.49*10-12
b) 6.84*10-9
c) 1.29*10-6
d) 2.29*10-4

11. The optical power at 20 MHz is 246.2 μW. Determine dc drive current applied to device with carrier recombination lifetime for LED of 6ns.
a) 3.48*10-4
b) 6.42*10-9
c) 1.48*10-3
d) 9.48*10-12

12. Determine the 3 dB electrical bandwidth at 3 dB optical bandwidth Bopt of 56.2 MHz.
a) 50.14
b) 28.1
c) 47.6
d) 61.96

13. The 3 dB electrical bandwidth B is 42 MHz. Determine 3dB optical bandwidth Bopt.
a) 45.18
b) 59.39
c) 78.17
d) 94.14

14. Determine degradation rate βrif constant junction temperature is 17 degree celsius.
a) 7.79*10-11
b) 7.91*10-11
c) 6.86*10-11
d) 5.86*10-11

15. Determine CW operating lifetime for LED with βrt = -0.58 and degradation rate βr = 7.86*10-11 h-1.
a) 32.12
b) 42
c) 22.72
d) 23.223

# Device Types

1. ____________ converts the received optical signal into an electrical signal.
a) Detector
b) Attenuator
c) Laser
d) LED

2. The first generation systems of optical fiber communication have wavelengths between ___________
a) 0.2 and 0.3 μm
b) 0.4 and 0.6 μm
c) 0.8 and 0.9 μm
d) 0.1 and 0.2 μm

3. The quantum efficiency of an optical detector should be high.
a) True
b) False

4. Which of the following does not explain the requirements of an optical detector?
a) High quantum efficiency
b) Low bias voltages
c) Small size
d) Low fidelity

5. How many device types are available for optical detection and radiation?
a) One
b) Two
c) Three
d) Four

6. The ___________ process takes place in both extrinsic and intrinsic semiconductors.
a) Avalanche multiplication
b) External photoemission
c) Internal photoemission
d) Dispersion

7. ____________ are widely used in first generation systems of optical fiber communication.
a) p-n diodes
b) 4-alloys
c) 3-alloys
d) Silicon photodiodes

8. Silicon has indirect band gap energy of __________________
a) 1.2 eV
b) 2 eV
c) 1.14 eV
d) 1.9 eV

9. Which of the following detector is fabricated from semiconductor alloys?
a) Photoconductive detector
b) p-i-n detector
c) Photodiodes
d) Photoemission detectors

10. Silicon photodiodes provide high shunt conductance.
a) True
b) False

# Optical Detection Principles

1. P-n photodiode is forward biased.
a) True
b) False

2. The depletion region must be ____________ to allow a large fraction of the incident light to be absorbed in the device(photodiode).
a) Thick
b) Thin
c) Long
d) Inactive

3. The process of excitation of an electron from valence band to conduction band leaves an empty hole in the valence band and is called as ____________
a) Detection
b) Absorption
c) Degeneration of an electron-hole pair
d) Regeneration of an electron-hole pair
Answer: d) Regeneration of an electron-hole pair

4. __________________ always leads to the generation of a hole and an electron.
a) Repulsion
b) Dispersion
c) Absorption
d) Attenuation

a) Magnetic field
b) Electric field
c) Static field
d) Depletion region

6. Electric field in the depletion region should be high.
a) True
b) False

7. The photocurrent of an optical detector should be __________
a) Less
b) More
c) Linear
d) Non-linear

8. How many types of optical detectors are available?
a) One
b) Four
c) Two
d) Three

# Absorption

1. The absorption of photons in a photodiode is dependent on __________
a) Absorption Coefficient α0
b) Properties of material
c) Charge carrier at junction
d) Amount of light

2. The photocurrent in a photodiode is directly proportional to absorption coefficient.
a) True
b) False

3. The absorption coefficient of semiconductor materials is strongly dependent on __________
a) Properties of material
b) Wavelength
c) Amount of light
d) Amplitude

4. Direct absorption requires assistance of photon.
a) True
b) False

5. In optical fiber communication, the only weakly absorbing material over wavelength band required is?
a) GaAs
b) Silicon
c) GaSb
d) Germanium

a) 3.01 μm
b) 2.09 μm
c) 0.92 μm
d) 1.09 μm

7. The semiconductor material for which the lowest energy absorption takes place is?
a) GaAs
b) Silicon
c) GaSb
d) Germanium

8. The wavelength range of interest for Germanium is __________
a) 0.8 to 1.6 μm
b) 0.3 to 0.9 μm
c) 0.4 to 0.8 μm
d) 0.9 to 1.8 μm

9. A photodiode should be chosen with a ________________ less than photon energy.
a) Direct absorption
b) Band gap energy
c) Wavelength range
d) Absorption coefficient

10. ________________ photodiodes have large dark currents.
a) GaAs
b) Silicon
c) GaSb
d) Germanium

11. For fabrication of semiconductor photodiodes, there is a drawback while considering _________________
a) GaAs
b) Silicon
c) GaSb
d) Germanium

12. _________________ materials are potentially superior to germanium.
a) GaAs
b) Silicon
c) GaSb
d) III – V alloys

13. ____________ alloys such as InGaAsP and GaAsSb deposited on InP and GaSb substrate.
a) Ternary
b) Quaternary
c) Gain-guided
d) III – V alloys

14. _________________ alloys can be fabricated in hetero-junction structures.
a) InGaSb
b) III – V alloys
c) InGaAsP
d) GaAsSb

15. The alloys lattice matched to InP responds to wavelengths up to 1.7μm is?
a) InAsSb
b) III – V alloys
c) InGaSb
d) InGaAs

# Quantum Efficiency, Responsivity and Long – Wavelength Cut-Off

1. The fraction of incident photons generated by photodiode of electrons generated collected at detector is known as ___________________
a) Quantum efficiency
b) Absorption coefficient
c) Responsivity
d) Anger recombination

2. In photo detectors, energy of incident photons must be ________________ band gap energy.
a) Lesser than
b) Greater than
c) Same as
d) Negligible

3. GaAs has band gap energy of 1.93 eV at 300 K. Determine wavelength above which material will cease to operate.
a) 2.431*10-5
b) 6.424*10-7
c) 6.023*103
d) 7.234*10-7

4. The long cutoff wavelength of GaAs is 0.923 μm. Determine bandgap energy.
a) 1.478*10-7
b) 4.265*10-14
c) 2.784*10-9
d) 2.152*10-19

5. Quantum efficiency is a function of photon wavelength.
a) True
b) False

6. Determine quantum efficiency if incident photons on photodiodes is 4*1011 and electrons collected at terminals is 1.5*1011?
a) 50%
b) 37.5%
c) 25%
d) 30%

7. A photodiode has quantum efficiency of 45% and incident photons are 3*1011. Determine electrons collected at terminals of device.
a) 2.456*109
b) 1.35*1011
c) 5.245*10-7
d) 4.21*10-3

8. The quantum efficiency of photodiode is 40% with wavelength of 0.90*10-6. Determine the responsivity of photodiodes.
a) 0.20
b) 0.52
c) 0.29
d) 0.55

9. The Responsivity of photodiode is 0.294 AW-1at wavelength of 0.90 μm. Determine quantum efficiency.
a) 0.405
b) 0.914
c) 0.654
d) 0.249

10. Determine wavelength of photodiode having quantum efficiency of 40% and Responsivity of 0.304 AW-1.
a) 0.87 μm
b) 0.91 μm
c) 0.88 μm
d) 0.94 μm

11. Determine wavelength at which photodiode is operating if energy of photons is 1.9*10-19J?
a) 2.33
b) 1.48
c) 1.04
d) 3.91

12. Determine the energy of photons incident on a photodiode if it operates at a wavelength of 1.36 μm.
a) 1.22*10-34J
b) 1.46*10-19J
c) 6.45*10-34J
d) 3.12*109J

13. Determine Responsivity of photodiode having o/p power of 3.55 μm and photo current of 2.9 μm.
a) 0.451
b) 0.367
c) 0.982
d) 0.816

14. Determine incident optical power on a photodiode if it has photocurrent of 2.1 μA and responsivity of 0.55 A/W.
a) 4.15
b) 1.75
c) 3.81
d) 8.47

15. If a photodiode requires incident optical power of 0.70 A/W. Determine photocurrent.
a) 1.482
b) 2.457
c) 4.124
d) 3.199

# Semiconductor Photodiodes Without Internal Gain

1. The width of depletion region is dependent on ___________ of semiconductor.
a) Doping concentrations for applied reverse bias
b) Doping concentrations for applied forward bias
c) Properties of material
d) Amount of current provided
Answer: a) Doping concentrations for applied reverse bias

2. Electron-hole pairs are generated in ___________
a) Depletion region
b) Diffusion region
c) Depletion region
d) P-type region

3. The diffusion process is _____________ as compared with drift.
a) Very fast
b) Very slow
c) Negligible
d) Better

4. Determine drift time for carrier across depletion region for photodiode having intrinsic region width of 30μm and electron drift velocity of 105 ms-1.
a) 1×10-10 Seconds
b) 2×10-10 Seconds
c) 3×10-10 Seconds
d) 4×10-10 Seconds

5. Determine intrinsic region width for a photodiode having drift time of 4×10-10 s and electron velocity of 2×10-10ms-1.
a) 3×10-5M
b) 8×10-5M
c) 5×10-5M
d) 7×10-5M

6. Determine velocity of electron if drift time is 2×10-10s and intrinsic region width of 25×10-6μm.
a) 12.5×104
b) 11.5×104
c) 14.5×104
d) 13.5×104

7. Compute junction capacitance for a p-i-n photodiode if it has area of 0.69×10-6m2, permittivity of 10.5×10-13Fcm-1 and width of 30μm.
a) 3.043×10-5
b) 2.415×10-7
c) 4.641×10-4
d) 3.708×10-5

8. Determine the area where permittivity of material is 15.5×10-15Fcm-1 and width of 25×10-6 and junction capacitance is 5pF.
a) 8.0645×10-5
b) 5.456×10-6
c) 3.0405×10-2
d) 8.0645×10-3

9. Compute intrinsic region width of p-i-n photodiode having junction capacitance of 4pF and material permittivity of 16.5×10-13Fcm-1 and area of 0.55×10-6m2.
a) 7.45×10-6
b) 2.26×10-7
c) 4.64×10-7
d) 5.65×10-6

10. Determine permittivity of p-i-n photodiode with junction capacitance of 5pF, area of 0.62×10-6m2 and intrinsic region width of 28 μm.
a) 7.55×10-12
b) 2.25×10-10
c) 5×10-9
d) 8.5×10-12

11. Determine response time of p-i-n photodiode if it has 3 dB bandwidth of 1.98×108Hz.
a) 5.05×10-6sec
b) 5.05×10-7Sec
c) 5.05×10-7sec
d) 5.05×10-8Sec

12. Compute maximum 3 dB bandwidth of p-i-n photodiode if it has a max response time of 5.8 ns.
a) 0.12 GHz
b) 0.14 GHz
c) 0.17 GHz
d) 0.13 GHz

13. Determine maximum response time for a p-i-n photodiode having width of 28×10-6m and carrier velocity of 4×104ms-1.
a) 105.67 MHz
b) 180.43 MHz
c) 227.47 MHz
d) 250.65 MHz

14. Determine carrier velocity of a p-i-n photodiode where 3dB bandwidth is1.9×108Hz and depletion region width of 24μm.
a) 93.43×10-5
b) 29.55×10-3
c) 41.56×10-3
d) 65.3×10-4

15. Compute depletion region width of a p-i-n photodiode with 3dB bandwidth of 1.91×108and carrier velocity of 2×104ms-s.
a) 1.66×10-5
b) 3.2×10-3
c) 2×10-5
d) 2.34×104

# Semiconductor Photodiodes With Internal Gain

1. ___________ has more sophisticated structure than p-i-n photodiode.
a) Avalanche photodiode
b) p-n junction diode
c) Zener diode
d) Varactor diode

2. The phenomenon leading to avalanche breakdown in reverse-biased diodes is known as _______
a) Auger recombination
b) Mode hopping
c) Impact ionization
d) Extract ionization

3. _______ is fully depleted by employing electric fields.
a) Avalanche photodiode
b) P-I-N diode
c) Varactor diode
d) P-n diode

4. At low gain, the transit time and RC effects ________
a) Are negligible
b) Are very less
c) Dominate

5. At high gain, avalanche buildup time ________
a) Is negligible
b) Very less
d) Dominates

6. Often __________ pulse shape is obtained from APD.
a) Negligible
b) Distorted
c) Asymmetric
d) Symmetric

7. Fall times of 1 ns or more are common.
a) False
b) True

8. Determine Responsivity of a silicon RAPD with 80% efficiency, 0.7μm wavelength.
a) 0.459
b) 0.7
c) 0.312
d) 0.42

9. Compute wavelength of RAPD with 70% efficiency and Responsivity of 0.689 A/w.
a) 6μm
b) 7.21μm
c) 0.112μm
d) 3μm

10. Compute photocurrent of RAPD having optical power of 0.7 μw and responsivity of 0.689 A/W.
a) 0.23 μA
b) 0.489 μA
c) 0.123 μA
d) 9 μA

11. Determine optical power of RAPD with photocurrent of 0.396 μAand responsivity of 0.49 A/w.
a) 0.91 μW
b) 0.32 μW
c) 0.312 μW
d) 0.80 μW

12. Determine the Responsivity of optical power of 0.4μW and photocurrent of 0.294 μA.
a) 0.735
b) 0.54
c) 0.56
d) 0.21

13. Compute multiplication factor of RAPD with output current of 10 μAand photocurrent of 0.369μA.
a) 25.32
b) 27.100
c) 43
d) 22.2

14. Determine the output current of RAPD having multiplication factor of 39 and photocurrent of 0.469μA.
a) 17.21
b) 10.32
c) 12.21
d) 18.29

15. Compute the photocurrent of RAPD having multiplication factor of 36.7 and output current of 7μA.
a) 0.01 μA
b) 0.07 μA
c) 0.54 μA
d) 0.9 μA

# Mid Infrared and Far Infrared Photodiodes

1. In the development of photodiodes for mid-infrared and far-infrared transmission systems, lattice matching has been a problem when operating at wavelengths ____________
a) 1 µm
b) Greater than 2 µm
c) 2 µm
d) 0.5 µm
Answer: b) Greater than 2 µm

2. What is generally used to accommodate a lattice mismatch?
a) Alloys
b) Attenuator
d) APD array

3. HgCdTe material system is utilized to fabricate long-wavelength photodiodes.
a) True
b) False

4. Avalanche photodiodes based on HgCdTe are used for ______________ in both the near and far infrared.
a) Dispersion
b) Dislocation
c) Ionization
d) Array applications

5. The detection mechanism in ____________ relies on photo excitation of electrons from confined states in conduction band quantum wells.
a) p-i-n detector
b) Quantum-dot photo detector
c) p-n photodiode
d) Avalanche photodiodes

6. When determining performance of a photo detector ___________ is often used.
a) No. of incident photon
b) No. of electrons collected
c) Responsivity
d) Absorption coefficient

7. The important parameter for exciting an electron with energy required from valence band to conduction band is?
a) Wavelength
b) Absorption coefficient
c) Responsivity
d) Band gap energy

8. __________ is less than or unity for photo detectors.
a) Absorption coefficient
b) Band gap energy
c) Responsivity
d) Quantum efficiency

9. There must be improvement in __________ of an optical fiber communication system.
a) Detector
b) Responsivity
c) Absorption Coefficient
d) Band gap energy

# Phototransistors and Metal – Semiconductor – Metal Photodetectors

1. The _____________ is photosensitive to act as light gathering element.
a) Base-emitter junction
b) Base-collector junction
c) Collector-emitter junction
d) Base-collector junction and Base-emitter junction

2. A large secondary current _________________ in n-p-n InGaAs phototransistor is achieved.
a) Between base and collector
b) Between emitter and collector
c) Between base and emitter
d) Plasma
Answer: b) Between emitter and collector

3. _______ emitter-base and collector-base junction capacitances is achieved by use of hetero-structure along with _________ base resistance.
a) Low, high
b) High, low
c) Low, low
d) High, negligible

4. A ________ is created by hetero-junction at collector-base junction.
a) Potential barrier
b) Depletion region
c) Parasitic capacitance
d) Inductance

5. Phototransistors based on hetero-junction using _________ material are known as waveguide phototransistors.
a) InGaP
b) InGaAs
c) InGaAsP/ InAlAs
d) ErGaAs

6. A phototransistor has collector current of 18 mA, incident optical power of 128 μW with a wavelength of 1.24 μm. Determine an optical gain.
a) 1.407 *102
b) 19.407 *102
c) 2.407 *102
d) 3.407 *102

7. For a phototransistor having gain of 116.5, wavelength of 1.28 μm, optical power 123μW. Determine collector current.
a) 0.123 mA
b) 0.0149 mA
c) 1.23 mA
d) 0.54 mA

8. The detection mechanism in the ____________ photo-detector includes inter sub-band transitions.
a) Dwell
b) Set
c) Avalanche
d) Futile

9. Which of the following is the difference between the n-p-n and conventional bipolar transistor?
a) Electric property
b) Magnetic property
c) Unconnected base
d) Emitter base efficiency

10. The n-p-n hetero-junction phototransistor is grown using ______________
a) Liquid-phase tranquilizers
b) Liquid-phase epistaxis
c) Solid substrate
d) Hetero poleax

11. The _____________ at emitter-base junction gives good emitter base injection efficiency.
a) Homo-junction
b) Depletion layer
c) Holes
d) Hetero-junction

12. Waveguide phototransistors utilize a ___________ waveguide layer under the _________ transistor region.
a) Active, passive
b) Passive, active
c) Homo, hetero
d) Hetero, homo

13. What is the main benefit of the waveguide structure over conventional hetero-junction phototransistor?
a) High depletion region
b) Depletion width
c) Increased photocurrent, responsivity
d) Low gain

14. Waveguide structure provides high quantum efficiency.
a) True
b) False

15. Metal-semiconductor-metal (MSM) photo-detectors are photoconductive detectors.
a) True
b) False

# Noise

1. _____________ refers to any spurious or undesired disturbances that mask the received signal in a communication system.
a) Attenuation
b) Noise
c) Dispersion
d) Bandwidth

2. How many types of noise are observed because of the spontaneous fluctuations in optical fiber communication systems?
a) One
b) Four
c) Two
d) Three

3. ______________ is caused due to thermal interaction between the free electrons and the vibrating ions in the conduction medium.
a) Thermal noise
b) Dark noise
c) Quantum noise
d) Gaussian noise

4. A small leakage current still flows from the device terminals even if there is no optical power incident on the photo detector.
a) True
b) False

5. ___________ distribution provides the description the random statistics of light emitted in black body radiation.
a) Poisson
b) Cumulative
c) Probability
d) Bose-Einstein

6. The probability of zero pairs being generated when a light pulse is present is given by which of the following equation?
a) P(0/1) = exp(-Zm)
b) P(x) = exp (Zm)
c) P(y) = x (0) + x(1)
d) P(z) = P(-Zm)

7. The minimum pulse energy needed to maintain a given bit-error-rate (BER) which any practical receiver must satisfy is known as ___________
a) Minimal energy
b) Quantum limit
c) Point of reversed
d) Binary signaling

8. A digital optical fiber communication system requires a maximum bit-error-rate of 10-9. Find the average number of photons detected in a time period for a given BER.
a) 19.7
b) 21.2
c) 20.7
d) 26.2

9. For a given optical fiber communication system, P(e) = 10-9, Zm = 20.7, f = 2.9×1014, η = 1. Find the minimum pulse energy or quantum limit.
a) 3.9×10-18
b) 4.2×10-18
c) 6.2×10-14
d) 7.2×10-14

10. An analog optical fiber system operating at wavelength 1μmhas a post-detection bandwidth of 5MHz. Assuming an ideal detector and incident power of 198 nW, calculate the SNR (f = 2.99×1014Hz).
a) 46
b) 40
c) 50
d) 52

11. The incident optical power required to achieve a desirable SNR is 168.2nW. What is the value of incident power in dBm?
a) -37.7 dBm
b) -37 dBm
c) – 34 dBm
d) -38.2 dBm

12. In the equation given below, what does τstands for?

Zm = ηP0τ/hf

a) Velocity
b) Time
c) Reflection
d) Refractive index

1. Which are the two main sources of noise in photodiodes without internal gain?
a) Gaussian noise and dark current noise
b) Internal noise and external noise
c) Dark current noise & Quantum noise
d) Gaussian noise and Quantum noise
Answer: c) Dark current noise & Quantum noise

2. The dominating effect of thermal noise over the shot noise in photodiodes without internal gain can be observed in wideband systems operating in the range of ________
a) 0.4 to 0.5 μm
b) 0.8 to 0.9 μm
c) 0.3 to 0.4 μm
d) 0.7 to 0.79 μm
Answer: b) 0.8 to 0.9 μm

3. A silicon p-i-n photodiode incorporated in an optical receiver has following parameters:

Quantum efficiency = 70%
Wavelength = 0.8 μm
Dark current = 3nA
Incident optical power = 150nW.
Bandwidth = 5 MHz


Compute the photocurrent in the device.
a) 67.7nA
b) 81.2nA
c) 68.35nA
d) 46.1nA

4. In a silicon p-i-n photodiode, if load resistance is 4 kΩ, temperature is 293 K, bandwidth is 4MHz, find the thermal noise in the load resistor.
a) 1.8 × 10-16A2
b) 1.23 × 10-17A2
c) 1.65 × 10-16A2
d) 1.61 × 10-17A2

5. ________________ is a combination of shunt capacitances and resistances.
a) Attenuation
b) Shunt impedance
d) Thermal capacitance

6. ______________ is used in the specification of optical detectors.
a) Noise equivalent power
b) Polarization
c) Sensitivity
d) Electron movement

7. A photodiode has a capacitance of 6 pF. Calculate the maximum load resistance which allows an 8MHz post detection bandwidth.
a) 3.9 kΩ
b) 3.46 kΩ
c) 3.12 kΩ
d) 3.32 kΩ

8. The internal gain mechanism in an APD is directly related to SNR. State whether the given statement is true or false.
a) True
b) False

9. ____________ is dependent upon the detector material, the shape of the electric field profile within the device.
a) SNR
b) Excess avalanche noise factor
d) Noise power
Answer: b) Excess avalanche noise factor

10. For silicon APDs, the value of excess noise factor is between _________
a) 0.001 and 0.002
b) 0.5 and 0.7
c) 0.02 and 0.10
d) 1 and 2

11. __________ determines a higher transmission rate related to the gain of the APD device.
a) Attenuation
b) Gain-bandwidth product
c) Dispersion mechanism
d) Ionization coefficient

12. _________________ APDs are recognized for their high gain-bandwidth products.
a) GaAs
c) Germanium
d) Silicon

13. APDs do not operate at signal wavelengths between 1.3 and 1.6μm.
a) True
b) False

1. How many circuits are present in an equivalent circuit for the digital optical fiber receiver?
a) Four
b) One
c) Three
d) Two

2. __________ compensates for distortion of the signal due to the combined transmitter, medium and receiver characteristics.
a) Amplification
b) Distortion
c) Equalization
d) Dispersion

3. ____________ is also known as frequency-shaping filter.
a) Resonator
b) Amplifiers
c) Attenuator
d) Equalizer

4. The phase frequency response of the system should be ____________ in order to minimize inter-symbol interference.
a) Non-Linear
b) Linear
c) More
d) Less

5. Noise contributions from the sources should be minimized to maximize the receiver sensitivity.
a) True
b) False

6. How many amplifier configurations are frequently used in optional fiber communication receivers?
a) One
b) Two
c) Three
d) Four

7. How many receiver structures are used to obtain better receiver characteristics?
a) Two
b) One
c) Four
d) Three

8. The high-impedance front-end amplifier provides a far greater bandwidth than the trans-impedance front-end.
a) True
b) False

9. A high-impedance amplifier has an effective input resistance of 4MΩ. Find the maximum bandwidth that may be obtained without equalization if the total capacitance is 6 pF and total effective load resistance is 2MΩ.
a) 13.3 kHz
b) 14.2 kHz
c) 15.8 kHz
d) 13.9 kHz

10. A high-input-impedance amplifier has following parameters (Total effective load resistance = 2MΩ, Temperature = 300 K). Find the mean square thermal noise current per unit bandwidth for the high-impedance configuration.
a) 8.9×10-27A2/Hz
b) 8.12×10-27A2/Hz
c) 8.29×10-27A2/Hz
d) 8.4×10-27A2/Hz

11. The mean square thermal noise current in the trans-impedance configuration is _________ greater than that obtained with the high-input-impedance configuration.
a) 30
b) 20
c) 15
d) 10

12. The major advantage of the trans-impedance configuration over the high-impedance front end is ______________
a) Greater bandwidth
b) Less bandwidth
c) Greater dynamic range
d) Less dynamic range

13. The trans-impedance front end configuration operates as a __________ with negative feedback.
a) Current mode amplifier
b) Voltage amplifier
c) Attenuator
d) Resonator

# FET Pre – Amplifiers

1. ____________ is the lowest noise amplifier device.
a) Silicon FET
b) Amplifier-A
c) Attenuator
d) Resonator-B

2. FET device has extremely high input impedance greater than _________
a) 107 Ohms and less than 108
b) 106 Ohms and less than 107
c) 1014 Ohms
d) 1023 Ohms

3. The properties of a bipolar transistor are superior to the FET.
a) True
b) False

4. Bipolar transistor is more useful amplifying device than FET at frequencies _____________
a) Above 1000 MHz
b) Equal to 1 MHz
c) Below 25 MHz
d) Above 25 MHz

5. High-performance microwave FETs are fabricated from ___________
a) Silicon
b) Germanium
c) Gallium arsenide
d) Zinc

6. Gallium arsenide MESFETs are advantageous than Silicon FETs.
a) True
b) False

7. The PIN-FET hybrid receivers are a combination of ______________
a) Hybrid resistances and capacitances
b) Pin photodiode and low noise amplifier (GaAs MESFETs)
c) P-N photodiode and low noise amplifier (GaAs MESFETs)
d) Attenuator and low noise amplifier (GaAs MESFETs)
Answer:b) Pin photodiode and low noise amplifier (GaAs MESFETs)

8. PIN-FET hybrid receiver is designed for use at a transmission rate of _____________
a) 130 Mbits-1
b) 110 Mbits-1
c) 120 Mbits-1
d) 140 Mbits-1

9. It is difficult to achieve higher transmission rates using conventional __________
a) Voltage amplifier
b) Waveguide Structures
d) MESFET

10. Which receiver can be fabricated using PIN-FET hybrid approach?
c) High-impedance front-end
d) Low-impedance front-end

11. A silicon p-i-n photodiode utilized with the amplifier and the receiver is designed to accept data at a rate of ___________
a) 276Mbits-1
b) 274 Mbits-1
c) 278Mbits-1
d) 302Mbits-1

12. What is usually required by FETs to optimize the figure of merit?
a) Attenuation of barrier
b) Matching with the depletion region
c) Dispersion of the gate region
d) Matching with the detector

1. How many design considerations are considered while determining the receiver performance?
a) Three
b) Two
c) One
d) Four

2. FET preamplifiers provide higher sensitivity than the Si-bipolar device.
a) True
b) False

3. What is the abbreviation of HBT?
a) Homo-junction unipolar transistor
b) Homo-junction bipolar transistor
c) Hetero-junction bipolar transistor
d) Hetero-Bandwidth transcendence

4. What type of receivers are used to provide wideband operation, low-noise operation?
b) Optoelectronic integrated circuits (OEICs)

5. ___________ circuits extends the dynamic range of the receiver.
a) Monolithic
b) Trans-impedance
c) Automatic Error Control (AEC)
d) Automatic Gain Control (AGC)

6. The sensitivity of the low-impedance configuration is ____________
a) Good
b) Poor
c) Great
d) Same as that of high-impedance configuration

7. What is generally used to determine the receiver performance characteristics?
a) Noise
b) Resistor
c) Dynamic range & sensitivity characteristics
d) Impedance
Answer:c) Dynamic range & sensitivity characteristics

8. The __________ technique eliminates the thermal noise associated with the feedback resistor in the trans-impedance front end design.
a) Compensation
b) Resonating impedance
c) Electromagnetic
d) Optical feedback

9. The removal of the feedback resistor in the optical feedback technique allows reciever sensitivity of the order of _______________
a) -54 dBm at 2Mbit/sec
b) -12 dBm at 2Mbit/sec
c) -64 dBm at 2Mbit/sec
d) -72 dBm at 2Mbit/sec

10. The optical feedback technique is useful at low transmission rates.
a) True
b) False

11. How many types of optical amplifier technologies are available.
a) One
b) Three
c) Four
d) Two

12. The optimum filter bandwidth is typically in the range ________________
a) 0.1 to 0.3 nm
b) 0.5 to 3 nm
c) 0.1 to 0.3 μm
d) 0.5 to 3 μm

# Optical Amplifiers – Semiconductor Optical Amplifiers

1. For linear as well as in nonlinear mode _______________ are most important network elements.
a) Optical amplifier
b) Optical detector
c) A/D converter
d) D/A converters

2. The more advantages optical amplifier is ____________
a) Fiber amplifier
b) Semiconductor amplifier
c) Repeaters
d) Mode hooping amplifier

3. ________________ cannot be used for wideband amplification.
a) Semiconductor optical amplifier
b) Erbium-doped fiber amplifier
c) Raman fiber amplifier
d) Brillouin fiber amplifier

4. ____________ is used preferably for channel selection in a WDM system.
a) Semiconductor optical amplifier
b) Erbium-doped fiber amplifier
c) Raman fiber amplifier
d) Brillouin fiber amplifier

5. For used in single-mode fiber __________ are used preferably.
a) Semiconductor optical amplifier
b) Erbium-doped fiber amplifier
c) Raman fiber amplifier
d) Brillouin fiber amplifier

6. Mostly ____________ are used in nonlinear applications.
a) Semiconductor optical amplifier
b) Erbium-doped fiber amplifier
c) Raman fiber amplifier
d) FPAs

7. _______________ is superior as compared to _________________
a) TWA, FPA
b) FPA, TWA
c) EDFA, FPA
d) FPA, EDFA

8. ______________ are operated at current beyond normal lasing threshold current, practically.
a) Semiconductor optical amplifier
b) Erbium-doped fiber amplifier
c) Raman fiber amplifier
d) Brillouin fiber amplifier

9. An uncoated FPA has peak gain wavelength 1.8μm, mode spacing of 0.8nm, and long active region of 300 v. Determine RI of active medium.
a) 4.25×106
b) 3.75×107
c) 3.95×107
d) 4.25×109

10. Determine the peak gain wavelength of uncoated FPA having mode spacing of 2nm,and 250μmlong active region and R.I of 3.78.
a)2.25×10-4
b)4.53×10-8
c)1.94×10-6
d)4.25×109

11. An SOA has net gain coefficient of 300, at a gain of 30dB. Determine length of SOA.
a) 0.32 m
b) 0.023 m
c) 0.245 m
d) 0.563 m

12. An SOA has length of 35.43×10-3m, at 30 dB gain. Determine net gain coefficient.
a) 5.124×10-3
b) 1.12×10-4
c) 5.125×10-3
d) 2.15×10-5
Answe: c) 5.125×10-3

13. An SOA has mode number of 2.6, spontaneous emission factor of 4, optical bandwidth of 1 THz. Determine noise power spectral density.
a) 1.33×10-3
b) 5.13×1012
c) 3.29×10-6
d) 0.33×10-9