Optical Communications Multiple Choice Questions on “Multicarrier Systems”.
1. A major attribute of coherent optical transmission was its ability to provide _______________ for future multicarrier systems and networks.
a) Attenuation
b) Dispersion
c) Frequency selectivity
d) Noisy carriers
Answer: c
Explanation: A coherent optical transmission involves the wavelength, frequency and the distance as its main factors. It provides frequency and wavelength selectivity with narrow channel spacing’s for future multicarrier systems and networks.
2. The channel width is narrow for the coherent systems than the WDM systems.
a) True
b) False
Answer: a
Explanation: The coherent optical systems involve wavelength selectivity with narrow channel spacing. The conventional WDM systems use a far more relaxed channel spacing than the coherent systems.
3. The technique within the coherent multicarrier systems used to broadcast the optical signals over the network is the use of passive _____________
a) Star coupler
b) Optical resonator
c) Optical regenerator
d) Local oscillator
Answer: a
Explanation: In multicarrier systems, the channels are separated via various techniques. The use of passive star coupler ensures that the optical signals are broadcasted over the network within the coherent system.
4. Estimate the minimum transmitter power if number of photons per bit are 150, wavelength 1.3 micrometer with an optical bandwidth of 20 THz.
a) 0.2 mW
b) 0.5mW
c) 1 mW
d) 2.3mW
Answer: b
Explanation: The minimum transmitter power is given by –
Ptx = Np hf B
Here, Ptx = transmitter power, f = frequency, h = Planck’s constant and B = bandwidth.
5. The performance degradation due to nonlinear phase noise is referred to as _____________
a) Munich effect
b) Linear bipolar effect
c) Gordon Mollenauer effect
d) Delta effect
Answer: c
Explanation: The phase noise is a variant due to the RZ signal. The nonlinear phase noise causes severe performance degradation in terms of bandwidth and frequency.
6. ______________ facilitates the doubling of the feasible spectral efficiency through the transmission of independent information in each of the two orthogonal polarizations.
a) WDM
b) Gordon Mollenauer effect
c) EDFA control
d) POLMUX
Answer: d
Explanation: POLMUX is abbreviated as Polarization multiplexing. It provides a different approach to the multilevel modulation. It requires polarization control at the receiver side.
7. ____________ is a transparent multiplexing technique.
a) POLMUX
b) PDM
c) WDM
d) Munich
Answer: a
Explanation: It is a transparent technique as it is not dominated by polarization mode dispersion or polarization-dependant loss. It provides many advantages to the multilevel modulation format in comparison to the non-POLMUX signals at the same data rate.
8. Which of the following is not a drawback of POLMUX?
a) Polarization-sensitive detection at the receiver
b) Receiver complexity
c) Cross-polarization nonlinearities
d) Multilevel modulation
Answer: d
Explanation: The drawbacks of the POLMUX include receiver complexity, polarization sensitivity at the receiver side and the cross polarization nonlinearities. It is advantageous to the multilevel modulation scheme.
9. A multicarrier modulation format in which there has been growing interest to compensate for impairments in optical fiber transmission systems is _______________
a) OFDM
b) EDM
c) WDM
d) ADM
Answer: a
Explanation: OFDM is abbreviated as orthogonal frequency division multiplexing. It combats both fiber chromatic dispersion and polarization mode dispersion.
10. It is suggested that the technique with high white noise is an attractive option for use in long haul systems.
a) False
b) True
Answer: a
Explanation: Long haul systems require a technique which boosts the distance covered by the signals with less use of carrier signal. The technique which exhibits high spectral density is an attractive option for the long haul systems.
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