B.TechSemester 52024-25Optical CommunicationBEC057

Optical Communication (BEC057) - AKTU Question Paper 2024-25

B.Tech · Semester 5 · Free PDF Download

This is the official AKTU Optical Communication Previous Year Question Paper for B.Tech Semester 5, academic session 2024-25. Published by Dr. A.P.J. Abdul Kalam Technical University (AKTU/UPTU), Lucknow. Free PDF download — no login required.

Course:B.Tech

Semester:Semester 5

Session:2024-25

University:AKTU / UPTU

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Questions Asked in 2024-25

Optical Communication (BEC057) — complete question paper · 70 marks · 3 Hours

Section AAttempt all questions in brief. 2 x 07 = 14

a
Why does fiber optics promise to be the technology of choice f or local area network?
b
Calculate the velocity of light within glass having refractive index (n) equal to 1.5?
c
Specify three peak wavelengths for the transparent windows in modern optical fibers
d
Define the term Photoluminescence. 4 1
e
Suppose a laser diode radiates re d light with wavelength of 65 0 nm. Calculate the energy of a single photon?
f
How does photo diode converts li ght into electrical signal? 5 2
g
Differentiate between coherent and non-coherent detection technique. 5 2

Section BAttempt any three of the following: 07 x 3 = 21

a
Draw a block diagram of fiber optic communications system an d describe the function of each component
b
Define the term dispersion in optical fiber. How much will a light pulse spread after travelling along 5 km of a step index fiber whose numerical aperture is 0.275 and refractive index of the core is 1.487?
c
With suitable energy band diag ram explain the mechanisms of absorption, spontaneous, and stimulated emission in a compound semiconductor?
d
Explain the principle of operation of a quantum well laser d iode? 4 2
e
With suitable block diagram ex plain Wavelength Division Multiplexing technique in optical fiber communication?

Section CAttempt any one part of the following: 07 x 1 = 07

a
Write the significance of tot al internal reflection in an op tical fiber. The refractive index of core and cladding of a silica fiber are 1.4 8 and 1.46 respectively. Calculate the cri tical propagation angle? Find th e total acceptance angle of the fiber?
b
Write short notes on: i. Dispersion shifted and dispersion flattened fiber ii. Polarization mode dispersion
a
Explain basic techniques used to couple light from an LED in to an optical fiber? Calculate the power coupled into a step index mu ltimode fiber whose n 1 = 1.48 and whose n 2 = 1.46 if the surface light emitting diode (SLED) radiates 100 µW?
b
Draw a graph depicting the t ypical input-output relationship i n a l a s e r diode and explain what mechanisms determine the course of the graph?
a
With suitable diagram explain the working of edge light emit ting diode (ELED) and surface light emitting diode (SLED)?
b
Write short note on: i. Dark Current ii. Bit Error Rate
a
How does responsivity depend on the wavelength of an optical signal? The responsivity of a photodiode is 0.85 A/W and the input powe r saturation is 1.5 mW. Calculate the photocurrent if the inciden t power is
b
Write the major advantages of Avalanche Photo Diode over p-i -n photodiode
a
What do you mean by mode coupling? Explain the various irregularities in the fiber of its causes
b
Draw a functional block diagra m of a receiver and briefly ex plain the function of each component?

Question text is extracted from the official AKTU question paper PDF above. Hindi translations are omitted — every question is printed in English in the original paper. Last verified: 2026-08-23.