Carrier-frequency-doubled photonic microwave vector signal generation based on PDM-MZM

Abstract

A simple method based on an integrated polarization-division multiplexing Mach–Zehnder modulator (PDM-MZM) to produce a carrier-frequency-doubled vector signal is presented and experimentally demonstrated. In this structure, the upper sub-MZM is driven by I/Q signals and biased at the quadrature point to modulate a baseband vector signal on the optical carrier. The lower sub-MZM is driven by a LO signal and is biased at the maximum transmission point (MATP) to generate the optical carrier and second-order sidebands. By filtering the negative second-order sideband via an optical bandpass filter (OBPF) and suppressing the optical carrier via polarization controller (PC), a carrier-frequency-doubled vector signal is generated at the photodetector. Due to the adoption of LO frequency-doubled technique, the system’s requirement of a high-frequency LO is relaxed. In a proof-of-concept experiment, 300 MSym/s QPSK signal with a carrier frequency of 16 GHz is obtained by 8 GHz LO signal. Besides, 25-km fiber transmission of the generated QPSK signal is demonstrated. When the optical power obtained after fiber transmission is higher than -4 dBm, the BER after demodulation is less than 8×10−10. Moreover, generation of vector signal with other formats is verified.