Alignment monitoring of the pulse carver and data modulator for RZ-DPSK systems

A novel technique for monitoring the alignment status between the pulse carver and data modulator for return-tozero differential phase-shift keying 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.