Multifunctional all-optical signal processing scheme for wavelength-division-multiplexing multicast, wavelength conversion, format conversion, and all-optical encryption using hybrid modulation format exclusive-OR gates based on four-wave mixing in highly nonlinear fiber.

A multifunctional optical signal processing scheme for 10-Gbaud quadrature phase shift keying (QPSK) and binary phase shift keying (BPSK) signals based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF) is proposed. Wavelength-division-multiplexing (WDM) multicast, wavelength conversion, modulation format conversion, and hybrid modulation format exclusive-OR (HMF-XOR) logic gates are realized simultaneously by simulation. One-to-three WDM multicast of 20-Gbps QPSK signals are achieved paying the optical signal-to-noise ratio (OSNR) penalties <0.8  dB at the bit error rate (BER) of 10. The converted BPSK signals with high performance are obtained; they are generated from wavelength conversion of 10-Gbps BPSK and format conversion from 20-Gpbs QPSK. In the case of HFM-XOR logic gates, we discuss the extension application in all-optical encryption. Therefore, both theoretical analysis and simulation results are conducted to analyze the feasibility of the dual-channel all-optical encryption for QPSK and BPSK signals. The OSNR penalties of decrypted QPSK and BPSK signals at the BER of 10 are 1 dB and 0.7 dB, respectively. The concentrated constellations and clear eye diagrams indicate the high performance of decrypted signals.