![MCQs [2024]](https://engineeringinterviewquestions.com/wp-content/uploads/2021/02/Interview-Questions-2.png)
Optical Communications online quiz on “Wavelength Conversion and Optical Regeneration”.
1. ___________________ is defined as a process by which the wavelength of the transmitted signal is changed without altering the data carried by the signal.
a) Wavelength conversion
b) Attenuation
c) Sigma management
d) Wavelength dispersion
Answer: a
Explanation: Wavelength conversion observes the changes in the length of the wave. It does not proportionate with the data carried by the signal or wave.
2. The device which is used to perform wavelength conversion is called as ___________
a) Attenuator
b) Wavelength Gyrator
c) Wavelength Circulator
d) Wavelength translator
Answer: d
Explanation: Wavelength translator changes the frequency of the wave and hence it is also called as frequency changer. It does not affect the data carried by the wave.
3. A wavelength converter is termed as _______ if the converted wavelength is longer than the original signal wavelength.
a) Down converter
b) Up converter
c) Attenuator
d) Shifter
Answer: b
Explanation: A wavelength converter is capable of receiving an incoming signal at any wavelength at the input port and produces output at the output port. A converter is termed as up converter when the output signal wavelength is longer than the original signal wavelength.
4. The ___________ converters cannot process different modulation formats.
a) Shifting
b) Optoelectronic wavelength
c) Opt-circular
d) Magnetic simulating
Answer: b
Explanation: In optoelectronic wavelength converters, the information contained in the intensity, frequency, phase of the signal is required to be reprocessed for the purpose of wavelength conversion. It does not process all the modulation formats.
5. The optical medium, in case of optical wavelength conversion is ___________
a) Depleted
b) Linear
c) Non-linear
d) Dispersive
Answer: c
Explanation: The implementation of optical wavelength conversion involves non-linearity of the optical medium. It can be either active or passive, each providing different nonlinear effects.
6. The process of imposing the nonlinear response of the medium onto the control signal is known as ______________ scheme.
a) Demodulation
b) Absorption
c) Cross-modulation
d) Repeater mixing
Answer: c
Explanation: The cross-modulation scheme involves changes produced due to the intensity variation of the intensity-modulated input signal. It takes place in the active cavity.
7. How many approaches are adopted by the cross-modulation scheme?
a) Four
b) Three
c) Two
d) Five
Answer: a
Explanation: Based on the properties of the nonlinear medium, the cross-modulation scheme can be divided into four main approaches. These are cross-gain modulation, cross-phase modulation, cross-absorption modulation, differential polarization modulation.
8. __________ wavelength converters make use of a passive optical medium to exploit non-linear effects.
a) Bipolar
b) Optoelectronic
c) Magnetic
d) Coherent
Answer: d
Explanation: The nonlinear effects include four-wave mixing and difference frequency generation. Coherent wavelength converters use a passive medium to extend the changes of nonlinear effects.
9. A _____________ wavelength converter utilizes the nonlinear properties of a semiconductor optical amplifier to perform the conversion process.
a) Cross-gain modulation
b) Cross-phase modulation
c) Cross-absorption modulation
d) Differential polarization modulation
Answer: a
Explanation: Cross-gain modulation wavelength converter is also called as XGM wavelength converter. It uses semiconductor optical amplifier(SOA) along with its nonlinear properties for the conversion process.
10. The intensity modulated data on one signal wavelength is called as _______
a) Dispersed data
b) Pump signal
c) Probe signal
d) Frequency signal
Answer: b
Explanation: Pump signal is intensity modulated data. It produces variations in the carrier density within the SOA which provides inverted gain modulation in the SOA medium.
11. The probe signal is inverse to that of the pump signal.
a) True
b) False
Answer: a
Explanation: The gain modulations of the pump signal are imprinted onto the probe signal. Thus, the probe signal acquires the inverse copy of the pump signal, thereby contributing to the wavelength conversion with the pump signal.
12. In the XGM converter, the transfer function maintains the rectangular shape.
a) True
b) False
Answer: b
Explanation: By default, the ideal transfer function should be rectangular in shape. But it does not apply the same for XGM converter as the amplitude gradually decreases.
13. The speed of operation of XGM wavelength conversion is determined by the _______________ of the SOA.
a) Depletion level
b) Hole concentration
c) Carrier dynamics
d) Electron concentration
Answer: c
Explanation: The carrier dynamics deals with the interaction time between the input and the probe signal. On increasing the interaction time, the speed of operation of XGM wavelength conversion is increased.
14. ____________ is defined as the deviation in the emission frequency with respect to time when a laser is driven by a time-varying current source.
a) Intensity probe
b) Dispersion
c) Attenuation
d) Frequency chirp
Answer: d
Explanation: Frequency chirp occurs during the process of XGM and XPM. It is often termed as instantaneous frequency variation.
15. When frequency chirp shifts the optical frequency towards the shorter wavelength, it is known as ________
a) Red shift
b) Green shift
c) Yellow shift
d) Blue shift
Answer: d
Explanation: When frequency chirp shifts the optical frequency towards the shorter wavelength, it is known as blue shift. Similarly, when frequency chirp shifts the optical frequency towards the longer wavelength, it is known as red shift.
.