All-optical OOK to 16 QAM modulation format conversion employing nonlinear optical loop mirror

摘要

This paper describes an all-optical on-off keying (OOK) to 16 quadrature amplitude modulation (QAM) format converter using nonlinear optical loop mirror (N0LM) based on cross-phase modulation (XPM) and parametric amplification in optical fibers. The 16 QAM signal is generated by the superposition of two quadrature phase shift keying (QPSK) signals with different amplitudes. OOK to QPSK modulation format conversion is achieved by XPM in one highly nonlinear fiber (HNLF). The amplitude ratio 2:1 of two QPSK signals can be realized by parametric gain in another HNLF, thanks to the phase matching condition which cannot be satisfied between lights with contrary direction of propagation. The flexibility of this converter is confirmed at the symbol rate of 10Gs/s by numerical simulation results with the length of 2~7-1 pseudo random binary sequence (PRBS) input OOK signals. The performance of this converter is also discussed.