All-Optical XOR Gate for QPSK In-Phase and Quadrature Components Based on Periodically Poled Lithium Niobate Waveguide for Photonic Coding and Error Detection Applications

摘要

An all-optical scheme based on periodically poled lithium Niobate waveguide (PPLN) for signal processing of the in-phase (I) and quadrature (Q) components of an input quadrature phase shift keying (QPSK) signal is presented. The device is able to work on the I and Q components without any additional demodulation stage and makes use of cascaded second harmonic and difference frequency generation (SHG and DFG respectively) in the PPLN waveguide to obtain the logical operation XOR(I,Q). A single continuous wave pump signal is needed in addition to the input signal to generate the output signal, in which the information is coded in a binary phase shift keying (BPSK) modulation. The logical XOR(I,Q) is a basic operation that can enable data coding and error detection in all-optical networks. Bit error rate measurements are provided to evaluate the system performance for a 20Gb/s DQPSK input signal, and tunability of the output signal wavelength has been attested with almost constant optical signal-to-noise-ratio (OSNR) penalty along the C-band.