Real-time 127-Gb/s coherent PM-QPSK transmission over 1000km NDSF with >10 cascaded 50GHz ROADMs

This paper describes experimental demonstration of 50GHz ROADM tolerance for a realtime, single-carrier, 127-Gb/s coherent PM-QPSK system. 10 WSSs are cascaded over 1000km NDSF and <;0.5dB OSNR penalty is measured for the worst case. Cascading limit is also predicted.