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Ece 522: Photonic Devices And Optical Communications Question Paper

Ece 522: Photonic Devices And Optical 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 OPTICAL FIBRE COMMUNICATIONS
CAT II

Answer ALL questions
1.
a. With the aid of a diagram explain the principle of operation of a Fabry-Perot semiconductor amplifier. (5mks)

b. The Erbium Doped Fibre Amplifier (EDFA) is sometimes said to operate like a LASER without mirrors. With the aid of a simple energy level diagram, explain the principle of operation of an EDFA that uses a 1480 nm pump LASER to amplify a 1550 nm optical signal. (5mks)

c. A fibre with an attenuation factor of 0.2 dB/km is used in a linke where Erbium Doped Fibre Amplifier is used to regenerate the signal after propagation for 50 km. What should be the gain of the EDFA required to maintain no-loss-no-gain regeneration? (3mks)

2.
a. Discuss the advantages of the p-i-n photodiode over p-n structure in a photodiode. (4mks)

b.
i. Define and explain the meaning of responsivity (R) and quantum efficiency of a photodetector.
ii. Derive the relationship between the responsivity and quantum efficiency of a photodetector at a given wavelength. (6mks)

c. A detector has a quantum efficiency of 10% at a wavelength of 500 nm. At a wavelength of 750 nm, the responsivity is twice the value at 500 nm. What is the quantum efficiency at 750 nm?

d. If at least 500 photons must be received on average for given detection performance and the fibre used has an attenuation of 0.6 dB/km and the transmission power coupled to the fibre is 5 mW. Assuming all the received photons can be detected and the wavelength is 1.5 micrometres, what is the upper limit for the bit rate if the length of the fibre is 30 km (4mks)

Ece 522: Photonic Devices And Optical Communications Question Paper

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