Polarisation-independent all-optical circulating shift register based on self-phase modulation of semiconductor optical amplifier

The authors propose and experimentally demonstrate polarisation-independent all-optical circulating shift register (CSR) based on self-phase modulation of a semiconductor optical amplifier, which is very insensitive to the polarisation of the input pulse train and requires very low switching energy (~176 fJ). An all-optical 91 bit CSR was constructed for an input pulse stream at 2.897 GHz, and a high extinction ratio of 20 dB or more was obtained