Fiber Optic Communication (FOC) important questionsMost repeated in SPPU papers
These 21 questions appeared in more than one SPPU Fiber Optic Communication paper we have: 9 papers, from Feb 2023 to Nov 2025. The most-asked come first. Each one links to the papers it was asked in.
Repeated questions
Endsem questions (15)
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An optical fiber transmission system is to be designed to operate on 8km length without repeaters. The rise time of the chosen components are source LED : 8ns, Fiber cable: intermodal :5ns/km, Intramodal: 1ns/km, Detector PIN :6ns Estimate maximum bit rate that may be achieved on the link when using NRZ and RZ formats.
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Let the data rate of 20mb/s and BER of 10-9. For the receiver PIN photodiode operating at 850 nm, the required receiver input signal is -42dBm .The LED is used as a source can couple 50uW(-l3dBm) average optical power into a fiber flylead with a 50 um core diameter. Assume 1dB loss occurs when the fiber flylead is connected to the cable and another 1dB connector loss at the cable-photo detector interface. System margin of 6dB.Let attenuation per km is 3.5dB/ km. Estimate link length.
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Insem questions (6)
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A double heterojunction InGAsP LED emitting at a peak wavelength of 1310 nm has radiative and non- radiative recombination times of 30 ns and 100 ns respectively. The drive current is 40 mA. Determine i) Bulk recombination lifetime ii) The internal quantum efficiency iii) Internal Power level
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Questions count as repeated when their wording matches closely across papers. Numericals that depend on a figure are left out, since the figure changes from paper to paper.