Optical time division demultiplexing using the gain saturation effect of semiconductor optical amplifier

Abstract

A novel model for an OTDM demultiplexer based on Cross Gain Modulation in a SOA is developed. Analysis is carried out to evaluate the performance of the OTDM demultiplexer in terms of output signal corresponding to '0' and 'I' bit of the desired OTDM channel. Expression is developed for the output signal current and noise currents when an optical direct detection receiver used to receive the demultiplexed signal. The expression for Signal to Noise Ratio and Extinction Ratio and BER are also derived. Performance results are evaluated numerically for operation at different bit rates of a particular channel considering Amplified Stimulated Emission (ASE) and photo detector (shot) and receiver (thermal) noise. The results are presented in terms of BER versus pump power at different bit rates for various input signal power level. The receiver sensitivity at specific BER and the output ER are also evaluated for different bit rate. It is found. that at a given signal input power the BER can be reduced by increasing the pump power and the required pump power is higher at higher level of input power. It is noticed that BER decreases with increase in pump power at a given signal power level. It is also found that at a given BER the required signal power is higher when the pump power is increased. It is clearly found that the required values of signal power are within the normal operational range of signal levels in a direct detection receiver. It is further, noticed that there is significant increase in extinction ratio at higher bit rate as it requires higher pump power at a given signal power at higher bit rates at a given BER (say, 10-9).