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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
FIRST SEMESTER M.TECH DEGREE EXAMINATION,
DECEMBER 2011

Branch: Electronics and Communication

Microwave and TV Engineering

01 EC 621 1 : Optical Communication
Systems Answer any twofull
questions from each part

Limit answers to the required points.

Max. Marks: 60 Duration: 3 hours

PARTA

1. a.Explain various non-linear effects occur in optical fibers.
6

b. An optical signal at a specific wavelength has lost 50%

of its power after 3traversing 3 Km of fiber. What is the
attenuation in dB/ Km of this fiber.

2. a.With necessary diagrams explain the design features of an
edge emitting LED. 5

b. A heterojunction LED emitting at peak wavelength of 850 run has radiative and 4
non radiative recombination times of 25ns and 90ns
respectively. If the drive current is 35mA find the
internal quantum efficiency and internal power level.

3a. Explain the working of Avalanche Photo Diode. 4

b. A digital fiber optic link operating at 850nm requires a
maximum BER of 10-9 5Find the minimum incident optical
power Pi that must fall on the photodetector having
quantum efficiency 1 to achieve this BER at a data rate
of 100 Mbps for a simple binary level switching scheme.

PART B

4. a.With a block diagram explain briefly a digital
transmission link as an optical 4data link with
waveforms at each stage.

b. Make the power budget and calculate the maxi-mum

transmission distance for 5a 1550nm light wave system
operating at 100Mb/s and using an Laser for launching ٣