All-Optical Modulation Format Conversion Between OOK, QPSK, and 8QAM

Modulation format conversion is useful when the signal is transmitted through networks employing different modulation formats. It is also expected to increase the spectral efficiency and reduce power consumption in network nodes by applying all-optical signal processing to the modulation format conversion. In this paper, we propose an all-optical modulation format conversion system between on-off keying, quadrature phase-shift keying, and 8-ary quadrature amplitude modulation using optical nonlinear effects in semiconductor optical amplifier and optical threshold device. We also evaluate the conversion performances of the system by numerical simulation in terms of optical signal-to-noise ratio, optical signal power, and accumulated chromatic dispersion.