This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on “Multiplexing Strategies”.
1. What is the full form of ETDM?
a) Electronic tube di-cyclic mechanism
b) Electrical time division multiplexing
c) Emphasis tier division mechanism
d) Electrical tube dielectric medium
View Answer
Explanation: ETDM is the major baseband digital strategy. It allows for greater exploitation of available fiber bandwidth.
2. The practical limitations of the speed of electronic circuits have been pushed towards operational frequencies around ___________
a) 100 MHz
b) 120 MHz
c) 100GHz
d) 80 Hz
View Answer
Explanation: The speed of the circuitry in the fiber optic communication plays an important role in its performance. It is pushed around 100 GHz frequency allowing for 100 Gbit/s feasibility.
3. A strategy used for increasing the bitrate of digital optical fiber systems beyond the bandwidth capabilities of the drive electronics is known as ___________
a) Optical time division multiplexing
b) Electrical time division multiplexing
c) Frequency division multiplexing
d) Code division multiplexing
View Answer
Explanation: OTDM is favourable for long distance transmission of signal. It is designed to push the bitrate of the fiber systems beyond the bandwidth limits to gain performance.
4. ____________ semiconductor laser sources provide low duty cycle pulse streams for subsequent time multiplexing.
a) Diameter preferred
b) Mode locked
c) Divine
d) Depletion
View Answer
Explanation: Mode locked semiconductor laser sources were used at the transmitter side. They provide effective distribution of time multiplexing providing low duty cycle pulse streams.
5. ______________ are the devices which are employed to eliminate the laser chirp.
a) Optical intensity modulators
b) Demodulators
c) Circulators
d) Optical Isolators
View Answer
Explanation: Optical intensity modulators eliminate the laser chirp. This laser chirp may result in dispersion of the transmitted pulses as they propagate within the single mode fiber, thus limiting the achievable transmission distance.
6. _____________ provides operation at high transmission rate.
a) Optical intensity modulators
b) Demodulators
c) Circulators
d) Electro-absorption modulators
View Answer
Explanation: Electro-absorption modulators are employed at the transmitter and receiver sections. They provide operation at high transmission rate and for field trial.
7. In __________ the microwave frequency are modulated with an optical carrier and transmitted using a single wavelength channel.
a) Subcarrier multiplexing
b) TDM
c) FDM
d) Code division multiplexing
View Answer
Explanation: Optical Subcarrier multiplexing (SCM) is transmitted using a single wavelength channel. It enables multiple broadband signals to be transmitted over single-mode fiber.
8. Which of the following techniques is easy to implement?
a) Amplitude shift keying
b) Phase shift keying
c) Frequency shift keying
d) SCM
View Answer
Explanation: Frequency shift keying has an advantage of being simple to implement at the modulator as well as demodulator side. It is formed by up converting to a narrowband channel at high frequency employing frequency.
9. Which of the following is the disadvantage of SCM?
a) Source nonlinearity
b) Linearity
c) Distortion
d) Narrow bandwidth
View Answer
Explanation: The problem associated with SCM is source nonlinearity. The distortion caused by this becomes noticeable when several subcarriers are transmitted from a single optical source.
10. In CATV, the signal must be received with a carrier to noise ratio of between __________
a) 90 and 100 dB
b) 10 and 30 dB
c) 60 and 70 dB
d) 45 and 55 dB
View Answer
Explanation: The CATV multichannel spectrum tends to minimize the required bandwidth. The carrier to noise ratio must be between to avoid degradation of picture quality.
11. The IF signal can be input to a demodulator to recover the baseband signal.
a) True
b) False
View Answer
Explanation: The IF signal is obtained through SCM at the receive terminals. The baseband video signal in a CATV is obtained through IF signal by using it with a demodulator input.
Sanfoundry Global Education & Learning Series – Optical Communications.
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