Model Paper (Objective)
Optical Fiber Communication
Note: Answer of questions are in bold options
UNIT-3
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. Which process gives the laser its special properties as an optical source?
a) Dispersion
b) Stimulated absorption
c) Spontaneous emission
d) Stimulated emission
3. A perfect semiconductor crystal containing no impurities or lattice defects is called as
a) Intrinsic semiconductor
b) Extrinsic semiconductor
c) Excitation
d) Valence electron
4. Population inversion is obtained at a p-n junction by
a) Heavy doping of p-type material
b) Heavy doping of n-type material
c) Light doping of p-type material
d) Heavy doping of both p-type and n-type material
5. How many types of hetero-junctions are available?
a) Two
b) One
c) Three
d) Four
6. 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
7. 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
8. Injection laser have a high threshold current density of
a) 104Acm-2and more
b) 102Acm-2
c) 10-2Acm-2
d) 10-3Acm-2
9. 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.
10. 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.
11. Quantum well lasers are providing high inherent advantage over
a) Chemical lasers.
b) Gas lasers.
c) Conventional DH devices.
d) BH device.
12. 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.
13. 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
14. It is a resonant cavity formed by two parallel reflecting mirrors separated by a mirror separated by a medium such as air or gas
a) Optical cavity
b) Wheatstone’s bridge
c) Oscillator
d) Fabry-perot resonator
15. The absence of in LEDs limits the internal quantum efficiency.
a) Proper semiconductor
b) Adequate power supply
c) Optical amplification through stimulated emission
d) Optical amplification through spontaneous emission
16. 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 %
12. must be operated in stimulated emission region.
a) Injection laser
b) LED’s
c) Detector
d) Receiver
13. Coherent radiation is relatively
a) Parabolic
b) Elliptic
c) Directional
d) Rectangular
14. Which behavior may prove as a limitation for injection lasers and LED’s?
a) Isotropic
b) Radioactive
c) Thermal
d) Photosensitive
15 maximizes the received signal-to-noise ratio in the receiver circuitry.
a) Filter
b) Equalizer
c) Detector
d) Reflector
16. A regenerative repeater is called as
a) Repetitive repeater
b) Regenerator
c) Attenuator
d) Gyrator
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