Gain control in semiconductor optical amplifier

This thesis is concerned with the study of characteristics of commercial Semiconductor Optical Amplifiers-SOAs and their employment in GPONs for the purpose of packet equalization of upstream bursts in order to provide additional loss budget. Additional loss budget is aimed at facilitating the extension of GPONs to provide not only longer distance between central office and end user, but is also expected to increase the number of maximum users that can be connected to a single central office. The problem and the requirements of optical networks are described. After careful investigation into legal and technical dimensions of the situation such as use of certain wavelengths and EDFA’s inabilities, it is concluded that instead of EDFA or an Opto-electronic amplifier, an SOA should be considered for the purpose of employing as an optical amplifier installed in front of burst mode receiver at the central office. Commercial SOAs are used in order to investigate the limitations of SOA so that a suitable solution can be looked for within the functional constraints of the amplifier. The results of parametric measurements including input/output signal power, Gain and saturation are discussed; four different commercial SOAs are assessed with special emphasis on input power dynamics and gain response. The bit error rate -BER analysis is performed on SOAs in the context of the findings of parametric analysis of the SOAs. The effect of varying the input signal power on BER was observed. The receiver sensitivity for BER of 10-9 was measured for various SOA input power values. Power penalty imposed on receiver’s sensitivity, by saturation effects and noise is analysed