Novel Optical Access Scheme with 33% RZ-8PSK Downlink Signals Using Phase Equalization

A novel optical phase modulation signal, the 8 phase-shift keying (8PSK) signal with 33% return-to-zero (RZ) clock, is generated and transmitted in 30-Gb/s optical downlink for broadband optical access application. At the transmitter, the 33% RZ clock is generated by one single-arm Mach-Zehnder modulator, and 8PSK optical signals are generated by cascading three phase modulators. At the receiver, the 33% RZ clock is extracted, and the phase equalization method is used for restoring the original transmitted information.