Photonic Aggregation of Microwave Signals With Electro-Optic Modulation and Polarization Combination

A novel approach to the implementation of photonic aggregation of microwave signals using a single dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM) and a polarizer is proposed and experimentally demonstrated. Four binary phase shift keying (BPSK) microwave signals with an identical carrier frequency are aggregated into a single 16 quadrature amplitude modulation (16QAM) optical signal through phase and amplitude control at the DP-DDMZM and the polarizer. The aggregated optical signal is then transmitted over an optical fiber to an optical coherent receiver, where the BPSK signals are recovered by demodulating the aggregated optical signal. The approach is evaluated experimentally. Four BPSK microwave signals with an identical carrier frequency of 15 GHz and each having a symbol rate of 1 GBaud are aggregated to be a 16QAM optical signal. The constellation diagrams are measured to confirm the effectiveness of the aggregation process. To further increase the transmission capacity without using additional spectral resources, the employment of polarization division multiplexing (PDM) is studied, and the doubling in transmission capacity is confirmed.