1. How many categories of nonlinear effects are seen in optical fibers?
a) One
b) Two
c) Three
d) Four
Explanation: The nonlinear effects are separated on the basis of their characteristics. There are two such categories; one is scattering effect and the other is Kerr effect.
2. Which of the following is not related to Kerr effects?
a) Self-phase modulation
b) Cross-phase modulation
c) Four-wave mixing
d)Stimulated Raman Scattering
Explanation: Stimulated Raman Scattering is related to scattering. The other effects include modulation and mixing which are parts of Kerr effect.
3. Linear scattering effects are _______ in nature.
a) Elastic
b) Non-Elastic
c) Mechanical
d) Electrical
Explanation: Linear scattering effects are elastic because the scattered wave frequency is equal to incident wave frequency. Nonlinear scattering effects are purely inelastic.
4. Which thing is more dominant in making a fiber function as a bidirectional optical amplifier?
a) Core material
b) Pump source
c) Cladding material
d) Diameter of fiber
Explanation: Brillouin gain is always greater than Raman gain. It exists for light propagation in opposite direction to the pump source. Also Brillouin frequency shifts and gain bandwidth are much smaller than Raman. Raman amplification occurs for light propagating in either direction. Thus, pump source is more important in making a fiber function as bidirectional optical amplifier.
5. _________ semiconductor laser sources generally have broader bandwidths.
a) Injection
b) Pulsed
c) Solid-state
d) Silicon hybrid
Explanation: Pulsed semiconductor lasers have broader bandwidths. Therefore, these sources prove to be inefficient pump sources. They prove inefficient especially for narrow gain spectrum.
6. Nonlinear effects which are defined by the intensity – dependent refractive index of the fiber are called as ________
a) Scattering effects
b) Kerr effects
c) Raman effects
d) Tomlinson effects
Explanation: Kerr effects are nonlinear effects. Nonlinear effects are divided into scattering and Kerr effects. Scattering effects include scattering of phonon whereas Kerr effects include intensity refractive index parameters.
7. Self-phase modulation can be used for _____________
a) Enhancing the core diameter
b) Wavelength shifting
c) Decreasing the attenuation
d) Reducing the losses in the fiber
Explanation: Self phase modulation is related to phase change. It imposes a positive frequency sweep on the pulse which in turn enables wavelength or frequency shifting.
8. The beating between light at different frequencies or wavelengths in multichannel fiber transmission causes ________
a) Attenuation
b) Amplitude modulation of channels
c) Phase modulation of channels
d) Loss in transmission
Explanation:Phase modulation is related to frequency and wavelength shifting. In multichannel fiber transmission, phase modulation causes generation of modulation sidebands at new frequencies. This phenomenon is called as four-wave mixing.
9. What is different in case of cross-phase modulation from self-phase modulation?
a) Overlapping but same pulses
b) Overlapping but distinguishable pulses
c) Non-overlapping and same pulses
d) Non-overlapping but distinguishable pulses
Explanation: In cross phase modulation, variation in intensity of one pulse width modulates the refractive index of the fiber which causes phase modulation of the overlapping phases. In self-phase modulation, this phase modulation broadens the pulse spectrum.
10. _____________ results from a case of nonlinear dispersion compensation in which the nonlinear dispersion compensation in which the nonlinear chirp caused by self-phase modulation balances, postpones, the temporal broadening induced by group velocity delay.
a) Four wave mixing
b) Phase modulation
c) Soliton propagation
d) Raman scattering
Explanation: Soliton propagation is a nonlinear dispersion phenomenon. It limits the propagation distance that can be achieved when acting independently. It balances broadening of light pulse.