JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV OPTICAL COMMUNICATIONS Previous Question Paper (December - 2020 - R16)
Answer any five questions. All questions carry equal marks.
Main
Explain the following terms with respect to optical fiber:
Numerical Aperture
Answer
The Numerical Aperture (NA) is a dimensionless measure of the light-gathering capacity of an optical fiber. It represents the sine of the maximum angle at which incident light can be coupled into the fiber core to undergo total internal reflection. It is defined as:
where n1 is the refractive index of the core and n2 is the refractive index of the cladding.
Refractive index
Answer
The Refractive Index (n) is a fundamental optical property defined as the ratio of the speed of light in a vacuum (c) to the speed of light in the given medium (v). It determines the phase velocity of light through the fiber material.
In optical fibers, the core refractive index (n1) is always slightly higher than the cladding refractive index (n2) to facilitate total internal reflection.
Acceptance angle
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Critical angle
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Snell’s law
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Draw the schematic of conventional silica fiber structure and explain it.
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What are the different modes of fiber and explain them with neat diagrams.
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Explain signal loss or attenuation mechanism in optical fiber.
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A 50km optical fiber has an attenuation of 0.25dB/km at 1550nm. If 100μW of optical power launched into the power, show that the emerging power at the fiber output is 0.56μW.
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What are the different types of optical fiber connectors? Explain their functions.
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How pulse is spread due to group delay in optical fiber?
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Explain the V-groove splicing of optical fiber with neat diagram.
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Why losses occur at joints of optical fiber? How to avoid them?
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Draw the structure of surface emitting LED and explain its working.
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Derive the Laser diode rate equation and explain its different modes of operation.
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Draw the structure of APD and explain its operation.
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What are the different performance parameters of digital receiver? Explain them.
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Draw point to point to optical link and explain function of each block.
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What is WDM? How it is used in single mode optical fiber communication?
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