GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER-VI (NEW) EXAMINATION - WINTER 2020
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Subject Code:2161005 Date:01/02/2021Subject Name:Optical Communication
Time:02:00 PM TO 04:00 PM Total Marks: 56
Instructions:
- Attempt any FOUR questions out of EIGHT questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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Q.1 (a) Briefly describe the block diagram of Optical Communication System. 03
(b) Explain in brief the transmission windows of OC. 04
(c) Describe double crucible Method for fiber fabrication. 07
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Q.2 (a) Define the following w.r.to propagation modes in OFC: 03
- Transverse Propagation Constant
- V Number
- Group Velocity
(b) Compare Single Mode and Multi Mode fibers. 04
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(c) Describe fiber Bending Losses in brief. 07
Q.3 (a) Compare LED and LASER as fiber optic source. 03
(b) Determine the normalized frequency at 850 nm for a step index fiber has a core radius of 25µm, core refractive index of 1.48 and cladding refractive index of 1.46. How modes propagate in this fiber at 1320 nm and 1550nm. 04
(c) Describe different lensing schemes used in optical cable. 07
Q.4 (a) Compare SLED (Surface emitting) and ELED (Edge emitting) as fiber source. 03
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(b) A multimode graded index fiber exhibits total pulse broadening, 0.1 µsec over a distance of 12 km. Calculate (1) Optimum bandwidth on the link assuming no inter symbol interference. (ii) pulse broadening per unit length: 04
(c) Explain various losses taking place at fiber to fiber joints. 07
Q.5 (a) Explain in brief dark current noise in photo detector. 03
(b) Describe the structure of P-I-N photo detector in brief. 04
(c) Explain different techniques of splicing in brief. 07
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Q.6 (a) Briefly describe temperature effect on Gain of APD. 03
(b) Explain APD in brief. 04
(c) Derive the equation for the power launched from LED source in to a S.I. Fiber. 07
Q.7 (a) How will you measure intermodal dispersion in frequency domain? 03
(b) Mention the requirement of good optical switch. 04
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(c) Discuss optical power loss model for a point to point link. 07
Q.8 (a) How will you measure chromatic dispersion? 03
(b) Compare SOA and EDFPA. 04
(c) Briefly explain wavelength converter in optical components. 07
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