First demonstration of digital coherent transmission in a deployed ROADM network with a 120 Gbit/s polarization-multiplexed 64 QAM signal

Abstract

We demonstrate the add/drop operation and transmission of 120 Gbit/s (10 Gsymbol/s) polarization-multiplexed (PDM) 64 QAM digital coherent signals in a deployed ROADM network. By equalizing waveform distortions at the ROADM node with an FIR filter, the QAM signal was successfully add/drop-multiplexed, and transmitted over a 50 km ring network testbed with neighboring 9 × 10 Gbit/s OOK WDM data. This indicates the applicability of digital coherent systems to the deployed ROADM network based on 10 Gbit/s OOK, and its upgradability to 120 Gbit/s PDM-64 QAM.