Signal stability in periodically amplified fiber transmission systems using multiple quantum well saturable absorbers for regeneration

The use of multiple quantum well (MQW) saturable absorbers (SAs) for signal regeneration in periodically amplified fiber transmission systems is explored. A systematic study of signal destabilization resulting from incomplete saturation of MQW SAs used for regeneration, and of means of overcoming such destabilization, is presented. A computer model for MQW SAs, which considers the asymmetric Fabry-Pe´rot (AFP) cavity structure commonly employed to increase the contrast of such devices, is presented. The model is used to simulate nitrogen-implanted MQW SAs with < 5 ps recovery time in a transmission system. A comparison is made with results previously obtained for a 10 Gb/s standard single-mode fiber (SMF) recirculating loop transmission experiment using MQW SAs and temporary soliton propagation for signal regeneration. The simulations allow the benefits derived from the two parts of the regenerator to be identified, as well as their contributions to the destabilization of the propagating signal. The error-free transmission distance is improved from ∼ 2000 to > 7000 km when the two components are combined.