A novel method using half-symbol delay tap sampling technique for monitoring timing misalignment between data modulator and pulse carver in 33% duty-cycle return-to-zero on-off keying (RZ-OOK), 50% duty-cycle RZ-OOK, and carrier-suppressed RZ-OOK optical transmitters is proposed and experimentally demonstrated. The presented scheme is able to not only identify three RZ-OOK signals but also determine both the timing misalignment magnitude and direction. The effectiveness of the proposed scheme is validated by simulation and experiment in 10-Gbps optical systems, and its robustness against imperfections of the transmitter is also analyzed.
The paper presents a new pilot-aided scheme to measure quadrature imbalance between the I and Q branch caused by
imperfection of dual-parallel Mach-Zehnder modulator in a CO-OFDM transmission system. The method can accurately
calculate the imbalance, and we implement the compensation of quadrature imbalance in a 36G CO-OFDM Receiver
with applying GSOP algorithm.