OPTICAL FIBRE COMMUNICATION (OFC) MAY 2013 ELECTRONICS AND TELECOMMUNICATION SEMESTER 8
Con. 8209-13. (REVISED COURSE) GS-3268
(3 Hours) [Total Marks : 100]
N.B. : (1) Question No. 1 is Compulsory.
(2) Attempt any four questions out of remaining six questions.
(3) Assume suitable data wherever necessary.
| 1. (a) | Discuss the basic block diagram of optical communication system. | 5 |
| (b) | Draw the refractive index profile for the step index and graded index fiber. For | 5 |
| each type give typical core and cladding diameters. | ||
| (c) | Differentiate between spontaneous and stimulated emissions. | 5 |
| (d) | Derive expression for the responsivity of an intrinsic photodetector in terms of | 5 |
| quantum efficiency and wavelength. | ||
2. (a) | Draw refractive index profile of a graded index fiber and show with neat diagram | 10 |
| transmission of light through this fiber. Explain how GRIN fiber has transmission | ||
| bit rate much higher than multimode step index fiber. | ||
| (b) | Find the core radius necassary for single mode operation at 820nm of stop index | 10 |
| fiber with n1=1.482 and n2= 1.474. What is the numerical aperture and maximum | ||
| acceptance angle of this fiber ? Calculate the corresponding solid angle. | ||
3. (a) | List the importance factor responsible for power loss in optical fiber. Explain each | 10 |
| factor briefly. | ||
| (b) | Explain interamodal and intermodal dispersion. How does despersion affect the | 10 |
| transmission bandwidth of optical fibers. | ||
4. (a) | What is the basic principle on which optical sources work ? With the help of a | 10 |
| LED structure explain its working. | ||
| (b) | Draw the structure of Avalanche Photo Diode (ADP) along with the electric field | 10 |
| profile that exist in the various regions of ADP structure. Explain the working. | ||
5. (a) | Explain modified chemical vapour deposition (MVCD) method of fiber fabrication | 10 |
| in detail. | ||
| (b) | Discuss a popular non-destructive technique for attenuation measurement. | 10 |
6. (a) | Describe two methods of splicing individual fibers together. What are the | 10 |
| advantage and disadvantage of each method. | ||
| (b) | What are the desirable requirement of a good fiber optic connector ? What are | 10 |
| the lensing schemes for coupling improvement ? | ||
7. | Write short notes on any two :- | 20 |
| (a) OTDR | ||
| (b) Link Power Budget | ||
| (c) Coherent and Concoherent optical transmission. |
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