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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:2009

ECE 522: PHOTONIC DEVICES AND FIBRE OPTIC COMMUNICATIONS

The following constants are provided:
c = 3 x 10^8 m/s - speed of light
h = 6.6 x 10^-34 Js - Planck's constant.
e = 1.6 x 10^-19 C - charge of an electron

1.
a. Briefly explain why fibre optic communication is preferred in some communication networks over wireless channels despite its vulnerability to physical damage. (3mks)

b. Sketch a point-to-point DWDM communication system and indicate all the important components in the system. (6mks)

c. Name three types of light sources suitable for long distance fibre optic communications. Explain your choices. (3mks)

d. Briefly outline two advantages and two drawbacks of the semiconductor light enmiting diode (LED) for use as a light source in optical fibre communications. (4mks)

2.
a. List any four semiconductor materials used for photonic devices over the range 0.8 to 1.7 micrometre wavelength range. Give two reasons for their choice. (2mks)

b. With the aid of suitable simple diagrams describe the principle of operation of an edge emitting heterostructure Fabry Perot Laser. (4mks)

c. For the FP Laser above describe how electrical and optical confinement is achieved. (6mks)

d. The energy bandgap for lightly doped Gallium Arsenide at room temperature is 1.43 eV. When the material is heavily doped it is found that the lasing transitions involve "bandtail" states which effectively reduce the bandgap by 8%. Determine the difference in emission wavelength of the light between the lightly doped and this heavily doped case. (2mks)

Ece 522: Photonic Devices And Fibre Optic Communications Question Paper

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