All-optical Format Conversion from QPSK to PAM4 Based on Vector Phase-Sensitive Amplifiers

Format conversion technology is an effective way to improve the performances of optical networks. In this paper, an optical conversion system based on vector phase-sensitive amplifiers is proposed. The system realizes the conversion from one quadrature phase shift keying (QPSK) signal to one 4-level pulse amplitude modulation (PAM4) signal. Compared with traditional scalar phase-sensitive amplifier (PSA), it is more convenient to adjust the power ratio between the signal and idler generated by the four-wave mixing effect in vector PSA-based system. The bit error ratios and error vector magnitudes of the QPSK and converted PAM4 are estimated and analyzed.