This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on “Application of Optical Amplifiers “.
1. Which of the following is not a drawback of regenerative repeater?
d) Long haul applications
Explanation: The regenerative repeaters are useful in long haul applications. However, such devices increase the cost and complexity of the optical communication system. It act as a bottleneck by restricting the system operational bandwidth.
2. The term flexibility, in terms of optical amplifiers means the ability of the transmitted signal to remain in the optical domain in a long haul link. State whether the given statement is true or false.
3. How many configurations are available for employment of optical amplifiers?
Explanation: Optical amplifiers can be employed in three configurations. These are simplex mode, duplex mode, multi-amplifier configuration.
4. Repeaters are bidirectional. State whether the given statement is true or false.
5. It is necessary to ____________ the optical carriers at different speeds to avoid signal interference.
Explanation: Optical amplifiers are bidirectional. They operate in both directions at the same carrier wavelength. In order to avoid interference, the optical carriers should be intensity modulated.
6. The _________________ increases the system reliability in the event of an individual amplifier failure.
a) Simplex configuration
b) Duplex configuration
c) Serial configuration
d) Parallel multi-amplifier configuration
Explanation: The optical amplifiers with spectral bandwidths in the range 50 to 100 nm allow amplifiers to be more reliable than repeaters. The parallel multi-amplifier configuration increases system reliability and relaxes the linearity.
7. Which of the following is not an application of optical amplifier?
a) Power amplifier
b) In-line repeater amplifier
Explanation: Optical amplifiers have a wide variety of applications in the transmitter as well as receiver side. It is used as the power amplifier in the transmitter side and as preamplifier at the receiver side.
8. _________ reconstitutes a transmitted digital optical signal.
b) Optical amplifiers
Explanation: Optical amplifiers simply act as gain blocks on an optical fiber link. However, in contrast, the regenerative repeaters reconstitute a transmitted digital optical signal.
9. _____________ are transparent to any type of signal modulation.
b) Optical amplifiers
Explanation: The main benefit of acting as a gain block for optical amplifier is that it can be transparent to modulation bandwidth. However, both the noise and signal distortions are continuously amplified.
10. _________________ imposes serious limitations on the system performance.
a) Fiber attenuation
b) Fiber modulation
c) Fiber demodulation
d) Fiber dispersion
Explanation: The fiber dispersion calculation does not take into account the non-regenerative nature of the amplifier repeaters. In this, the pulse spreading and the noise is accumulated.
11. __________ is the ratio of input signal to noise ratio to the output signal to noise ratio of the device.
a) Fiber dispersion
b) Noise figure
c) Transmission rate
d) Population inversion
Explanation: Noise figure judges the performance factor of the devices. It is the in and out ratio of signal to noise degradation for any device.
12. How many factors govern the noise figure of the device?
Explanation: Noise figure is governed by factors such as the population inversion, the number of transverse modes in the amplifier cavity, the number of incident photons on the amplifier and the optical bandwidth of the amplified spontaneous emissions.
13. What is the typical range of the noise figure?
a) 1 – 2 dB
b) 3 – 5dB
c) 7 – 11 dB
d) 12 – 14 dB
Explanation: Typical noise figures range from 7 to 11 dB The SOAs are generally at the bottom end of the range and the fiber amplifiers towards the top end.
Sanfoundry Global Education & Learning Series – Optical Communications.
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