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

Abstract

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.