Matched Filter Design for RRC Spectrally Shaped Nyquist-WDM Systems

We investigate the matched filter design for root-raised-cosine (RRC) Spectrally Shaped Nyquist-WDM Systems. We show that the complexity of the receiver-side dynamic butterfly equalizer can be significantly reduced by incorporating a matched filter in the static chromatic dispersion equalizer for RRC Nyquist spectrally shaped signals. We find that the Nyquist-WDM system with a matched filter is sensitive to the laser frequency offset between the local oscillator at the receiver and the laser at the transmitter, and show that the frequency offset induced penalty decreases with increased RRC roll-off factor. With a roll-off factor of 0.1, the OSNR penalty at BER 10^-3 from 1 GHz frequency offset is less than 0.2 dB for 28-Gbaud PDM-QPSK, and less than 0.4 dB for 28-Gbaud PDM-16QAM.