Widely Tunable Burst Mode Digital Coherent Receiver With Fast Reconfiguration Time for 112 Gb/s DP-QPSK WDM Networks

A widely tunable burst mode digital coherent receiver is implemented in a 112 Gb/s DP-QPSK WDM system. The receiver performance is validated in a 24-channel WDM test-bed using a commercially available DS-DBR laser as the local oscillator. It is demonstrated that the wavelength tunable laser can switch to any one of the 24-channels in less than 130 ns, thus enabling the dynamic reception of 5 μ s optical bursts. The performance of the DS-DBR local oscillator laser is commensurate with burst mode coherent reception when differential decoding is employed and the parallel DSP implementation does not impair the polarization and frequency tracking performance of a digital coherent receiver under burst mode operation. The worst case reconfiguration time of the burst mode receiver, which is a combination of the laser switching time and the CMA convergence time, is less than 410 ns when switching from a single channel to any other channel in the WDM grid. It is shown that the variation in reconfiguration time is dependent on the convergence time of the CMA equalizer, which is adversely affected by certain input states of polarization.