Photonic generation of microwave frequency shift keying signals using a dual-polarization quadrature phase shift keying modulator

A novel method to generate microwave frequency shift keying (FSK) signals based on a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator is proposed and verified by a simulation. In this simulation work, the DP-QPSK modulator is employed to produce two orthogonally polarized double-sideband modulated signals with a wavelength spacing that is four times of the radio frequency driving frequency. Then, the signals are sent into a polarization modulator driven by a binary coding signal for complementary phase modulations. After that, a microwave FSK signal with frequency multiplication factors of four for bit ‘1’ and eight for bit ‘0’ is successfully generated through photodetection. The proposed system exhibits good stability and frequency tunability. Thanks to the high frequency multiplication factors, this method can find potential applications in high-frequency communication systems.