160-GBaud DQPSK Optical Time-Division Demultiplexing Using a Polarization Modulator

We propose and experimentally demonstrate a scheme for demultiplexing 160-GBaud differential quadrature phase shift keying optical time-division-multiplexing signals to 40-GBaud tributaries based on a polarization modulator (PolM) connected within a fiber loop. The PolM is used instead of a Mach–Zehnder modulator because the PolM reduces the insertion loss and is free from the bias drift problem since no DC bias is required. The generated optical gate is characterized with a pulsewidth of 5.4 ps, an extinction ratio larger than 15 dB, and a signal-to-noise ratio of over 28 dB at 40 GHz. Error-free performance is achieved with a power penalty of 1.8 dB in the worst case.