All-optical flip-flop with inproved extinction ratio using optical bistability of single mode fabry-perot laser diode

Abstract

All-optical flip-flops play an important role in future photonic networks such as optical burst switching and packet switching networks. They provide latching functions utilized for applications such as bit-length conversion, time-division multiplexing/demultiplexing, packet buffering, reshaping, and retiming. The current research on all-optical flip-flops is still in an early stage. Recently, many different technologies have been considered to store light. In our previous work, we achieved an all-optical flip-flop using two coupled Fabry- Perot laser diodes (FP-LDs); one of the two FP-LDs is an ordinary commercial FP-LD, and the other is an FP-LD specially designed with a built-in external cavity, operating in single longitudinal mode with high side mode suppression ratio (SMSR), this special FP-LD is called tunable single mode FP-LD. However, the flip-flop had a low extinction ratio (or called $\It{on-off contrast ratio}$) of about 7 dB. In this thesis, an all-optical flip-flop with improved extinction ratio is proposed and experimentally demonstrated. The key principle of the flip-flop is based on the inverted S-shaped bistability of injection-locked single mode Fabry-Perot laser diode (FP-LD). The flip-flop was realized using two coupled single mode FP-LDs; one of the two FP-LDs was used as a master LD, the other was used as a slave LD. Since only two single mode FP-LDs were used and connected directly with each other, the proposed flip-flop had a simple and cost-effective structure. The flip-flop was operated by separate set and reset pulses, which were external control signals. The control signals were generated by 1.4 Gbit/s NRZ pattern modulators. When a set pulse was injected into the flip-flop, the output of the flip-flop was in low power state ("off" state). And with the introduction of reset pulse, the flip-flop output was in high power state ("on" state). Due to such a set-reset operation, the flip-flop had an inverted latchable output. In the s...