An optical (Q)PSK-RF-signal transmitter based on two cascaded Mach-Zehnder modulators

This paper proposes an optical transmitter to generate phase-shift-keying (PSK) radio frequency (RF)-signal, using two cascaded single-drive Mach-Zehnder modulators (SDMZMs). With input of a continuous-wave (CW) light, an electrical non-return-to-zero (NRZ) data, and an RF-local oscillator (RF-LO) signal at a frequency of ωl, the transmitter can simultaneously produce three PSK signals and two CW tones on both sides in spectrum, by employing nonlinear modulation technique. With the help of optical filters, the desired signals can be selected to mix at a photodetector (PD) to obtain a PSK-RF-signal with the carrier frequency of ωl, 3ωl, or 5ωl. Our scheme can be easily extended to generate quadrature PSK-RF-signal. The feasibility of our proposal is experimentally and numerically verified.