Optical Communications Multiple Choice Questions on “Fiber and Waveguide Amplifiers”.
1. The spectral dependence on gain is always constant.
a) True
b) False
Answer: b
Explanation: The spectral dependence on gain is mostly not constant. Thus the spectral bandwidth for erbium-doped silica fibers is restricted to around 300 GHz.
2. ESA ________ the pumping efficiency of device.
a) Increases
b) Does not affects
c) Reduces
d) Has negligible effect on
Answer: c
Explanation: In erbium fiber amplifier photons at pump wavelength promotes the electrons in upper lasing level into a high state of excitation. These electrons decay non-radiate to intermediate levels and then back to upper lasing level thereby reducing pumping efficiency.
3. Signal amplification is obtained in ____________
a) Erbium-doped fluoro-zir-carbonate fiber multimode
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Brillouin fiber amplifier
Answer: a
Explanation: To avoid excited state absorption (ESA). We should use different glass technology in place by using a 488 nmpump wavelength; erbium-doped multimode fluoro zir carbonate fiber provides gain at 1.525 μmwavelengths.
4. It is possible to construct a single rare-earth-doped fiber amplifier which provides amplification for all-bands.
a) True
b) False
Answer: b
Explanation: Each material has different absorption emission properties to absorb energy either in single or multi steps. Also it possesses property to emit light in one or more narrow spectral ranges. Thus we cannot construct a single earth-doped fiber for all bands.
5. _______________ is constructed using erbium-doped glass.
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Brillouin fiber amplifier
Answer: a
Explanation: As compared to other glass, erbium-based micro fiber amplifier is more advantageous. This amplifier provides high optical gain over just a few centimeters of fiber over many meters.
6. ____________ uses Er3+-doped erbium glass.
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Brillouin fiber amplifier
Answer: a
Explanation: The erbium-based micro fiber amplifier uses Er3+-doped erbium glass. It supports the doping constructions of erbium ions at high levels as compared to conventional glasses.
7. The most advantageous amplification is ____________
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Brillouin fiber amplifier
Answer: c
Explanation: As compared to all the amplifications, Raman amplification is more advantageous. It has self-phase matching between pump of signal together with broad gain bandwidth as compared to other nonlinear processes.
8. _________ is also known as lump Raman amplifiers.
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Discrete Raman amplifiers
Answer: d
Explanation: Discrete Raman Amplifiers are lumped elements. This lumped element is to be inserted in transmission line to provide gain.
9. _______________ extends the pump power into transmission line fiber.
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Distributed Raman amplification
Answer: d
Explanation: In Distributed Raman amplification, all pump power is confined to lumped element. And it is distributed when the amplification takes place among several kilometers.
10. _____________ are called hybrid Raman amplifier.
a) Lumped and distributed Raman Amplifiers
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Distributed Raman amplification
Answer: a
Explanation: Lumped and distributed Raman Amplifiers can be combined together to be used in wideband application. This combination increases overall amplified spectral bandwidth.
11. In ___________ the ASE contributes most of noise.
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Distributed Raman amplification
Answer: d
Explanation: ASE contributes most of noise in Raman Amplification. The common sources of noise include beating of signal with ASE, mixing, self-phase modulation and cross-plane modulation.
12. In _____________ Rayleigh scattering can be reduced.
a) An erbium-based micro fiber amplifier
b) Rare-earth-doped fiber amplifiers
c) Raman fiber systems
d) Distributed Raman amplification
Answer: d
Explanation: Rayleigh scattering adverse effects can be reduced in Raman Amplification. This can be done by employing two or more stages of amplification over single stage amplification over fiber.
13. Compute the fiber nonlinear coefficient of a parametric optical amplifier having parametric peak gain of 63.6 dB, signal power of 1.6W, length 520.
a) 2.78×10-2 W-1km-1
b) 9.61×10-3 W-1km-1
c) 3.25×10-3 W-1km-1
d) 5.61×10-4 W-1km-1
Answer: b
Explanation: The fiber nonlinear coefficient can be found by
γ = Gp(dB)-log10(0.25)/Ppl×L × 1/10log10(2.718)2
= 63.6+6/1.6×1.6×520×1/8.7 = 9.61×10-3 W-1km-1.
14. Compute signal power for parametric amplifier having length of 500, nonlinear gain coefficient 12.6×10-3 W-1km-1 and parametric peak gain of 63.9 dB.
a) 0.245 W
b) 0.012 W
c) 0.19 W
d) 0.342 W