Practical Constraints of Coherent Transmission

Optical Communications

This set of Optical Communications Questions and Answers for Entrance exams focuses on “Practical Constraints of Coherent Transmission”.

1. Which technology development has helped the field of optical fiber communication?
a) Glass technology
b) Component technology
c) Multiplexing
d) Power

2. __________ dictates the performance characteristics required from components and devices which are to be utilized in coherent optical fiber systems.
a) System considerations
b) Bluetooth technology
c) Multiplexing
d) Practical constraints

3. Coherent optical transmission is degraded by the ________ associated with the transmitter and local oscillator lasers.
a) Phase noise
b) White noise
c) Dissipation
d) Power

4. ___________ improves the spectral purity of the device output and noise current.
a) Power dissipation
b) Laser line width reduction
c) Laser line width injection
d) Phase noise

5. ____________ is the principal cause of line width broadening in the coherent devices.
a) Electromagnetic field
b) Power dissipation
c) Injection laser phase noise
d) Gaussian noise

6. Which technique was started for narrowing of injection laser line widths?
a) External resonator cavity
b) Long-hauled oscillator
c) Circulator
d) Gyrator

7. The line width tolerance is wider for heterodyne receivers.
a) False
b) True

8. ___________ is an alternative to reduce phase noise and line width requirements.
a) Homodyne detection
b) Heterodyne detection
c) FSK modulation
d) Phase diversity reception

9. ______________ is the progressive spatial separation between the two polarization modes as they propagate along the fiber.
a) Fiber birefringence
b) Fiber dispersion
c) Fiber separation
d) Fiber coupling

10. How many compensator devices are required to provide full polarization-state control?
a) Three
b) One
c) Four
d) Two

11. Which technique was found to be providing an infinite range of polarization control?
a) Homodyne detection
b) Fiber squeezers
c) Heterodyne detection
d) Power dissipation

12. What is the main drawback of the squeezer?
a) Damages the fiber
b) Attenuation
c) Dispersion
d) Signal degradation

13. The use of balanced receiver compensates the losses due to coupling optics.
a) True
b) False

14. ___________ is the phenomenon which occurs in the single carrier systems due to small refractive index changes induced by the optical power fluctuations.
a) SBS gain
b) Self-phase modulation
c) FSK modulation
d) Birefringence

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