Design and analysis of cross phase modulation based all optical half subtractor using carrier reservoir semiconductor optical amplifier

Semiconductor optical amplifier (SOA) possesses nonlinear characteristics, which can be exploited to realize circuits such as adder, subtractor, parity generator and checker, encryption, decryption etc. However, conventional SOA suffers from slow carrier recovery; hence its use is not feasible for high-speed applications. Carrier reservoir (CR) SOA is a modified form of conventional SOA in which a carrier reservoir layer is grown near the active region to provide carriers, when stimulated emission depletes carriers in the active region leading to fast gain and phase recovery. This paper describes the modeling of CR-SOA and, subsequently implementation of CR-SOA based half subtractor at 100 Gb/s with a return to zero modulated signals. The performance of CR-SOA based half subtractor is evaluated through parameters like extinction Ratio, bit error rate, eye-opening factor and Quality factor, along with other key parameters such as data rate, amplified spontaneous emission (ASE) power and injection current. Performance comparison is made between CR-SOA based half subtractor and conventional SOA based half subtractor to validate the outperformance of the former at a high data rate.