# Optical Communications Questions and Answers – Optical Bistability, Digital Optics and Optical Computation

This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on “Optical Bistability, Digital Optics and Optical Computation”.

1. ___________ provides a series of optical processing functions.
a) Wavelength convertors
b) Wavelength amplifiers
c) Detectors
d) Bi-stable optical devices

Explanation: Optical bi-stable devices include optical logic and memory elements, A-D convertors. Their response to light is nonlinear giving the basis of optical communication.

2. ___________ comprise of Fabry-Perot cavity.
a) Wavelength convertors
b) Wavelength amplifiers
c) Bi-stable optical devices
d) Detectors

Explanation: Fabry-Perot cavity consists of a material in which there are variations in refractive index with optical intensity. These variations are nonlinear giving rise to bistability.

3. The optical path length in nonlinear medium is integer number of ______ wavelength.
a) Half
b) Double
c) Three-fourth
d) Single

Explanation: Fabry-Perot cavity exhibits a sharp resonance to optical power passing into and through it. This is achieved when optical path length is integer number of half wavelength in nonlinear medium.

4. As compared to laser, the value of _________ in the cavity controls the optical transmission.
a) Amplification
b) Refractive index
c) Rectification
d) Reflection

Explanation: The refractive index value in the Fabry-Perot cavity controls the optical transmission. This provides high optical output on resonance and low optical output off resonance.

5. ___________ are able to latch between two distinct optical states.
a) Wavelength converters
b) Wavelength amplifiers
c) Detectors
d) Bistable optical devices

Explanation: The transfer characteristic for Bistable optical devices exhibit two state hysteresis resulting from turning in and out of resonance. So they can be latched between two states responding to external signal acting as flip-flop.

6. __________ can act as AND, OR, NOT gate.
a) Wavelength converters
b) Wavelength amplifiers
c) Detectors
d) Bistable optical devices

Explanation: BOD’s exhibit 2-state hysteresis. Thus they are able to latch between two operating states (0 and 1) thereby providing logic functions.

7. _______ proves superior to _______
a) BOD’s, electronic devices
b) Electronic devices, BOD’s
c) BOD’s, convertors
d) Convertors, BOD’s

Explanation: There is also a thing of picosecond switching using only Pico-joules of energy. A BOD comprises of these switching properties. Thus, it proves superior to electronic devices.

8. ________ BOD’s provides optical feedback.
a) Extrinsic
b) Intrinsic
c) Detector
d) Bistable

Explanation: All optical or intrinsic devices which utilize a nonlinear optical medium between a pair of partially reflecting mirrors forming a nonlinear etalon in which feedback is provided optical.

9. ___________ devices employ artificial nonlinearity.
a) Extrinsic
b) Intrinsic
c) Hybrid
d) Bistable

Explanation: Hybrid devices have artificial nonlinearity in an electro-optic medium in the cavity. This produces variations in refractive index through electro-optic effect.

10. Hybrid devices have limited ________ speed.
a) Switching
b) Planar
c) Curvature
d) Electrical

Explanation: Hybrid BOD’s provides flexibility. But at the same time their switching speeds are limited by use of electrical feedback. These devices are interconnected to provide a more complex logic circuit.

11. _______ exhibit optical bistability.
a) Extrinsic lasers
b) Intrinsic lasers
c) Detectors
d) Semiconductor lasers

Explanation: Semiconductor lasers have optical bistability. This is due to nonlinearities in absorption, gain, dispersion, wave guiding and the selection of output polarization.

12. ___________ is fabricated with tandem electrode.
a) Full convertor
b) Semiconductor
c) Detector diode
d) Bistable laser diode

Explanation: Bistable laser diode is fabricated with tandem electrode. The tandem electrode provides two gain sections. Also it has a loss region between them.

13. Optical pulsing can be obtained using _________
a) BODs
b) WDM
c) Detector
d) Semiconductor

Explanation: BODs with a very narrow bi-stable loop can provide optical pulsing. This type of device can be used to shape, clean up and amplify a noisy input pulse.

14. A weak second beam is introduced in _________
a) BOD differential amplifier
b) WDM
c) Detector
d) Semiconductor laser

Explanation: A weak second beam in BOD differential amplifier is introduced into the nonlinear optical cavity. This is used to control the resonance and transmission of the main beam through effects of its own stored energy.

Sanfoundry Global Education & Learning Series – Optical Communications.

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