Alignment Monitoring of the Pulse Carver and Data Modulator for RZ-DPSK Ssystems

A novel technique for monitoring the alignment status between the pulse carver and data modulator for return-to-zero (RZ) differential phase-shift keying (DPSK) systems is proposed and demonstrated. The proposed technique utilizes a polarization- maintaining fiber, polarizer and power meter. Both the simulation and measurement results show that the proposed technique can monitor the bit-error-rate degradation caused by timing misalignment between the pulse carver and data modulator.