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G1048 Pages: 2

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SEVENTH SEMESTER B.TECH DEGREE EXAMINATION(S), MAY 2019

Course Code: EC405
Course Name: OPTICAL COMMUNICATION

PARTA
Answer any two full questions, each carries 15 marks.

Draw the block diagram of a light wave system. Mention the advantages of
Optical fiber Communication system.
Explain the working principle of laser action? How a semiconductor diode
functions like a laser diode?
Differentiate between spontaneous and stimulated emission.
Explain the mode theory for the propagation of light in optical fiber.
Explain the Modified Chemical Vapor Deposition process in fiber fabrication.
Explain the Numerical Aperture of an optical fiber with neat diagram. Calculate
the fractional index change for a given optical fiber if the refractive indices of the
core and cladding are 1.563 and 1.498 respectively. Also, calculate (i) numerical
aperture (ii) angle of acceptance in air.
PART B
Answer any two full questions, each carries 15 marks.

Briefly explain the different selection criteria for detectors using in optical

communication.

Draw the schematics of pin photodiodeand APD and explain its working.

What is meant by responsivity? How it is related to quantum efficiency?

A transmitter has an output power of 0.lmW. It is used with a fiber having
NA=0.25, attenuation of 6dB/Km and length 0.5 km. The link contains two
connectors of 2dB average loss. The receiver has a minimum acceptable power
(sensitivity) of -35dBm. The design has allowed a 4dB margin. Calculate the link

power budget.

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Duration: 3 Hours

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