Optical Communications Questions and Answers – Analog Systems

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This set of Optical Communications Multiple Choice Questions & Answers (MCQs) focuses on “Analog Systems”.

1. Determine dispersion equalization penalty if total RMS pulse broadening is 4.8ns, BT is 25 Mbits/s.
a) 0.03 dB
b) 0.08 dB
c) 7 dB
d) 0.01 dB
View Answer

Answer: a
Explanation: Dispersion equalization penalty is denoted by DL. It is given by-
DL = 2 (2σTBT√2)4. Here σT=RMS pulse broadening.
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2. Determine RMS pulse broadening with mode coupling if pulse broadening is 0.6 over 8km.
a) 1.6ns
b) 1.7ns
c) 1.5ns
d) 1.4ns
View Answer

Answer: b
Explanation: Total RMS pulse broadening with mode coupling is given by-
σT = σ√L. Here σT = RMS pulse broadening, L = length of the fiber.

3. Determine dispersion equalization penalty with mode coupling of 1.7ns if BT is 25 Mbits/s.
a) 4.8 * 104dB
b) 4 * 104dB
c) 4.2 * 104dB
d) 3.8 * 104dB
View Answer

Answer: c
Explanation: Dispersion equalization penalty is denoted by DL. With mode coupling, it is given by-
DL=2 (2σTBT√2)4. Here σT=RMS pulse broadening.

4. Determine dispersion equalization penalty without mode coupling if BT is 150 Mbits/s and total rms pulse broadening is 4.8ns.
a) 34 dB
b) 33 dB
c) 76.12 dB
d) 34.38 dB
View Answer

Answer: d
Explanation: Dispersion equalization penalty is denoted by DL(WM). It is given by-
DL(WM) = 2 (2σTBT√2)4. Here σT = RMS pulse broadening, (WM) = without mode coupling.

5. Determine ratio of SNR of coaxial system to SNR of fiber system if peak output voltage is 5V, quantum efficiency of 70%, optical power is 1mW, wavelength of 0.85μm.
a) 1.04 * 104
b) 2.04 * 104
c) 3.04 * 104
d) 4.04 * 104
View Answer

Answer: a
Explanation: Ratio of SNR of coaxial system to SNR of fiber system is given by-
Ratio = V2hc/2KTZ0ηPiλ. Here, η=quantum efficiency, Pi = 0ptical power in mW, V=optical output voltage.
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6. Determine the peak output voltage if efficiency is 70%, wavelength is 0.85μm and output power is 1mW.
a) 7V
b) 8V
c) 5V
d) 6V
View Answer

Answer: b
Explanation: Peak output voltage is given by-
V2 = (2KTZ0ηPiλ * Ratio)/hc. Here, η = quantum efficiency, Pi=0ptical power in mW, V=optical output voltage.

7. Determine the efficiency of a coaxial cable system at 17 degree Celsius with peak output voltage 5V, 0.85 μm wavelength and SNR ratio of 1.04 * 104.
a) 80%
b) 70%
c) 40%
d) 60%
View Answer

Answer: b
Explanation: The efficiency of a coaxial cable system is η=V2hc/2KTZ0ηPiλ * Ratio. Hereη=quantum efficiency, Pi = 0ptical power in mW, V=optical output voltage.

8. Determine the wavelength of a coaxial cable system operating at temperature 17 degree Celsius at output voltage of 5V, 100Ω impedance, optical power of 1mW, 70% quantum efficiency.
a) 0.39μm
b) 0.60μm
c) 0.85μm
d) 0.98μm
View Answer

Answer: c
Explanation: The wavelength can be determined by –
λ = V2hc/2KTZ0ηPi * Ratio. Hereη=quantum efficiency, Pi = 0ptical power in mW, V = optical output voltage.

9. Determine the impedance of a coaxial cable system operating at temperature 17 degree Celsius at output voltage of 5V, 0.85μmwavelength, optical power of 1mW, 70% quantum efficiency and SNR ratio of 1.04 * 104.
a) 80Ω
b) 50Ω
c) 90Ω
d) 100Ω
View Answer

Answer: d
Explanation: The impedance is given by-Z0=V2hc/2KTPi * Ratio. Hereη=quantum efficiency, Pi = Optical power in mW, V=optical output voltage.
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10. The 10-90% rise times for components used in D-IM analog optical link is given. (LED=10ns, Intermodal=9ns/km, Chromatic=2ns/km, APD = 3ns). Link is of 5km. Determine the total rise time.
a) 62ns
b) 53ns
c) 50ns
d) 52ns
View Answer

Answer: d
Explanation: Total rise time is given by-
Tsyst=1.1[Ts2+Tn2+Tc2+TD2]1/2. Here Ts = rise time, Tn = intermodal time, Tc = Chromatic time.

11. The 10-90% rise times for components used in D-IM analog optical link is given. (LED=10ns, Intermodal=9ns/km, Chromatic=2ns/km, APD = 3ns). Link is of 5km. It has an optical bandwidth of 6MHz. Determine maximum permitted system rise time.
a) 58.3ns
b) 54ns
c) 75ns
d) 43.54ns
View Answer

Answer: a
Explanation: The maximum permitted system rise time is given by-
Tsyst(Max) = 0.35/Bopt. Here, Bopt=Optical Bandwidth.

Sanfoundry Global Education & Learning Series – Optical Communications.

To practice all areas of Optical Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn