Hi Rajguru M Mohan.
I would like to mention that A travelling-wave model of a semiconductor optical amplifier based non-linear loop mirror is developed to investigate the importance of travelling-wave effects and gain/phase dynamics in predicting device behaviour. A constant effective carrier recovery lifetime approximation is found to be reasonably accurate (±10%) within a wide range of control pulse energies. Based on this approximation, a heuristic model is developed for maximum computational efficiency. The models are applied to a particular configuration involving feedback. Travelling wave soa is an optical amplifier which causes polarization sensitive type amplification by the occurrence of a change in the carrier density of its material when a weak optical signal is injected into it. The carrier density occurs by releasing some of the energies of its electrons in the form of photons to adjust with the initial wavelength of the weak optical signal. I hope this will be of some help to you.
Thanks