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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Seventh semester B.Tech examinations (S), September 2020

Course Code: EC405
Course Name: OPTICAL COMMUNICATION

PARTA
Answer any two full questions, each carries 15 marks.
Define macroscopic and microscopic bending losses.
Explain Outside Vapor Phase Oxidation fabrication process with neat diagram.
Compare it with MCVD process.
Explain different types of materials used for making optical fibers.
Define attenuation constant. Explain the different attenuation mechanisms in
optical fibers.
Explain the following i) total internal reflection ii) axial numerical aperture in a
graded index fiber.
Explain the working of surface emitting LED with neat diagram. Also explain its
emission pattern.
PART ‏تا‎
‎Answer any two full questions, each carries 15 marks.
Explain receiver sensitivity and quantum limit of detection of optical receiver.
In a coherent optical communication system operating on the basis of homodyne
detection, the received optical power is 2 nW and the signal bandwidth is 1 GHz.
Taking the quantum efficiency of the detection to be 0.8 and the wavelength as

1500 nm find the SNR in case of short noise limited performance.

With the help of necessary figures, describe the working of an IMDD system.
Explain the working of APD. What do you meant by reach through effect?

A photo detector generates a photo current of 0.25uA for an incident optical
power of 0.8uW at operating wavelength of 0.87um. Estimate the quantum
efficiency of photo detector at this wave length.

Derive the expressions for rise time and power budget analysis.

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Duration: 3 Hours

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