Code: A-24
Time: 3 Hours
Subject: OPTO ELECTRONICS AND
OPTICAL COMMUNICATIONS
Max. Marks: 100

NOTE: There are 11 Questions in all.

  • Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.
  • Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.
  • Any required data not explicitly given, may be suitably assumed and stated.
    _____________________________________________________________________
Q.1       Choose the correct or best alternative 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 cause 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

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