Design of all-optical gain-clamped lumped Raman fibre amplifier for optimal dynamic performance

The effect of lasing wavelength selection and optical feedback loop loss on the performance of an all-optical gain-clamped (AOGC) lumped Raman fibre amplifier (LRFA) is investigated both theoretically and experimentally. Suppression of surviving channel power fluctuations is selected as a criterion of the performance of the AOGC LRFA. A large-signal numerical model which incorporates time variation effects and the downstream propagation of signals, upstream propagation of pumps and downstream and upstream propagation of amplified spontaneous emission (ASE) spectral components has been used for the theoretical analysis. The LRFAs consist of 13 km of counter-directionally pumped dispersion compensating fibre (DCF). In the experiment, channel addition/removal is simulated by propagating optical power from two laser diodes through the AOGC LRFA. One of them is square-wave modulated at 500 Hz and the power fluctuations of the continuous wave signal of the other laser diode caused by cross-gain saturation effect in LRFAs are monitored.