Anna University Chennai 2005 B.E OPTO ELECTRONICS AND OPTICAL COMMUNICATIONS - Question Paper

Code: A-24
Time: three Hours Subject: OPTO ELECTRONICS AND
OPTICAL COMMUNICATIONS
Max. Marks: 100


NOTE: There are 11 ques. in all.
ques. one is compulsory and carries 16 marks. ans to Q. 1. must be written in the space given for it in the ans book supplied and nowhere else.
ans any 3 ques. every from Part I and Part II. every of these ques. carries 14 marks.
Any needed data not explicitly given, may be suitably presumed and said.
_____________________________________________________________________Q.1 select the accurate or best option in the following: (2x8)

a. The fiber core diameter for a single mode step index fiber which has a mode field diameter of 11.6m and the normalized frequency of 2.2 will be

(A)3.74 m.
(C) 5.04 m (B) 4.95 m.
(D) ) 6.18 m
b. A step index fiber has a solid acceptance angle in air of 0.115 radians and a relative refractive index difference of 0.9%. The speed of light in the fiber.

(A) 2.51x108 m/sec.
(C) 2x108 m/sec.
(B) 2.11x108 m/sec.
(D) 1.98x108 m/sec.
c.
A multimode step index fiber has a numerical aperture of 0.4 and core
refractive index of 1.48. The insertion loss at a joint caused by a 5° angular
mis-alignment will be

(A 0.64 dB
(C) 0.46 dB.
(B) 0.83 dB.
(D) 1.3 dB.
d. .The principal reason of linewidth broadening within the semiconductor laser is

(A) Phase Noise.
(C) Quantum Noise.
(B) White Noise.
(D) Thermal Noise.
e. A lens-coupled surface emitting LED launches 190 of optical power into a multimode step index fiber when a forward current of 25 mA is flowing through the device. If the forward voltage across the diode is 2.5 V, then the overall power conversion efficiency will be

(A) 0.4
(C) 0.3
(B) 0.5
(D) 0.6


f. An APD has a quantum efficiency of 45% at 0.85m . When illuminated with radiation of this wavelength, it produces an output photocurrent of 10A after avalanche gain with a multiplication factor of 250. The received optical power of the device will be
(A) 43.2 nW.
(C) 77.8 nW. (B) 54.6 nW.
(D) 23.5 W.
g. A 1.5 MHz info signal with a dynamic range of 64 mV is sampled quantized and encoded using a direct binary code. The quantization is linear with 512 levels. The maximum possible bit duration will be

(A) 23 ns.
(C) 37 ns.
(B) 32 ns
(D) ) 12 s.
h. The large bandwidth available with optical fiber communication is primarily due to

Earning:   Approval pending.