Optical Equalization of 42.7-Gbaud Band-Limited NRZ-DQPSK Signals for High-Spectral-Efficiency Transmission

We demonstrate the use of an optical equalizer to allow a 42.7-Gbaud (85.4-Gb/s) NRZ-DQPSK signal to tolerate the narrow optical filtering required in high-spectral-efficiency systems. The equalizer passbands are repetitive, enabling equalization of multiple channels.