DSP-Enabled Compensation of Demodulator Phase Error and Sensitivity Improvement in Direct-Detection 40-Gb/s DQPSK

We demonstrate a novel electronic compensation scheme for demodulator phase error in direct-detection 40-Gb/s DQPSK using a joint digital-signal-processing (DSP). Using data-aided multi-symbol-phase-estimation, the DSP-enabled receiver also affords an improved sensitivity over conventional hard-detection.