Optical phase‐sensitive amplification of higher‐order QAM signal with single Mach–Zehnder amplitude modulator

An optical phase‐sensitive amplifier (PSA) has the potential of low‐noise optical amplification. A frequency non‐degenerate PSA (ND‐PSA) can amplify arbitrary modulation formats including higher‐order QAM. The ND‐PSA requires a co‐propagating phase conjugated light (idler light) that has been conventionally created with an optical phase conjugator at the transmitter side. We propose a transmitter configuration using simultaneous signal generation of both a signal and its idler by double‐sideband modulation for transmission systems with ND‐PSAs. The proposed scheme provides a simple configuration with a single Mach–Zehnder amplitude modulator without optically creating the idler light. We performed experiments using 16QAM, 32QAM, and probabilistically shaped 256QAM signals. As a result, a phase‐sensitive amplification with each modulation format was successfully demonstrated using the proposed transmitter configuration.