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Ece 522: Photonic Devices And Fibre Optic Communications Question Paper

Ece 522: Photonic Devices And Fibre Optic Communications

Course:Bachelor Of Engineering In Electrical And Electronics Engineering

Institution: Moi University question papers

Exam Year:2012

MOI UNIVERSITY
DEPARTMENT OF ELECTRICAL AND COMMUNICATIONS ENGINEERING

ECE 522: PHOTONIC DEVICES AND FIBRE OPTIC COMMUNICATIONS

Answer ALL questions
1.
a. Sketch a diagram showing the essential components of a basic optical communication system and state the function of each of the components. (4mks)

b. Explain how the bandwidth of an optical fibre can be boosted by applying the Wavelentig Division Multiplexing (WDM) technique. (3mks)

2.
a. List and explain three important conditions that must be satisfied in order to achieve the successful operation of a semiconductor LASER. (6mks)

b. Based on your answer in 2(a) above, explain the difference between a semiconductor LED and a semiconductor LASER. (2mks)

3. If a fibre has an attenuation of 5dB/km and the power coupled from the light source, working at 1.5 micrometre, to the fibre is 10mW, determine:
i. The received power if the fibre has a length of 10 km
ii. The number of photons (if all are detected) in 1 ns (6mks)

4.
a. What measure of optical fibre quality does the numerical aperture (NA) give?

b. A step-index fiber has a core index of refraction of n1 = 1.425 and a cladding of refractive index n2. The cut-off angle for light entering the fibre from air is found to be 8.50 degrees.
i. Derive an expression for NA in terms of n1 and n2
ii. What is the value of NA of the fibre?
iii. Determine the index of refraction n2 of the cladding of this fibre. (9mks)
The following constants are provided:
c = 3*10^8 m/s - speed of light
h = 6.6*10^-34 Js - Planck's constant

Ece 522: Photonic Devices And Fibre Optic Communications Question Paper

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