All-optical circular shift register based on semiconductor optical amplifiers

We present a new and potentially integrable scheme to realize an all-optical circulating shift register consisting of a fiber-loop based optical buffer (OB) and an optical AND gate. The OB is implemented using semiconductor optical amplifier as a nonlinear element and the AND gate is realized by means of four wave mixing effect in a semiconductor optical amplifier. The operation of the shift register has been verified for a 10-bit input sequence at a sequence bit rate of 2.5 GHz and 10 GHz respectively. The simulation results show that \(\hbox {BER}=10^{-9}\) is achieved at optical signal-to-noise (OSNR) ratio of 16dB at the shift register output. The dependence of the output quality factor ( \(Q\) -factor) on SOA parameters is also investigated and discussed.