OPTICAL FIBRE COMMUNICATION (OFC) MAY 2011 ELECTRONICS AND TELECOMMUNICATION SEMESTER 8
(3 Hours) [Total Marks:-100]
Q.1 (a) What do you mean by direct and indirect band gap semiconductors? [5 Marks]
(b) Explain following terms: - [10 Marks]
i) Total Internal Reflection ii) Acceptance angle
iii) Critical angle iv) Quantum Efficiency
v) Responsivity
(c) Which are the different connection problems occur while jointing fibers. [5 Marks]
Q.2 (a) Discuss inter modal and intra modal dispersion. [10 Marks]
(b) Find critical radius of curvature at which large bending losses occur for a multimode fiber
with a core refractive index of 1.5, a refractive index difference of 3% and an operating
wavelength of 0.82µm. [10 Marks]
Q.3 (a) Explain linear and non-linear scattering losses. [12 Marks]
(b) Explain working principle of Avalanche Photo diode. [8 Marks]
Q.4 (a) Define :- (i) Bit error rate (ii) Quantum limit [5 Marks]
(b) Write advantages of optical fiber communication over conventional electrical
communication. [5 Marks]
(d) Compare surface and edge emitting LEDs. [5 Marks]
Q.5 (a) (i) Explain measurement of spectral loss in optical fiber using cutback technique. [6 Marks]
(ii) A 2km length of multimode fiber is attached to apparatus for spectral loss measurement.
The measured output voltage from photo receiver using the full 2km fiber length is 2.1 V
at a wavelength of 0.85µm. When the fiber is then cut back to leave a 2 m length the
output voltage increase to 10.7 V. Determine the attenuation per kilometer for the
fiber at a wavelength of 0.85 µm. [4 Marks]
Q.6 (a) How preamplifiers used in optical fiber communication receivers are classified. Explain
different types. [10 Marks]
(b) Discuss how numerical aperture is measured using scanning photo detector and rotating
stage method. [10 Marks]
Q.7 Write note on(any two):- [20 Marks]
i) Splicing Techniques
ii) Fabrication techniques (List all Methods and explain one method only)
iii) Optical Fiber Communication System
iv) OTDR
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