Optical Subcarrier Processing for Nyquist SCM via Coherent Spectrum Overlapping in FWM with Coherent Pump

We propose coherent spectrum overlapping through FWM with coherent multi-carrier pump, for coherently combining low-level subcarriers to high-level ones in Nyquist SCM. 16QAM subcarriers are obtained with <1dB sensitivity variation and no error floor at up to 10−5 BER.