Sub-Nyquist Field Trial Using Time Frequency Packed DP-QPSK Super-Channel Within Fixed ITU-T Grid

TL;DR

This paper demonstrates a sub-Nyquist time frequency packing technique in a field trial for super-channel transmission over long distances, achieving high spectral efficiency with low-order modulation formats in a real-world environment.

Contribution

First implementation of sub-Nyquist time frequency packing in a super-channel field trial over long-haul, showing effective spectral efficiency with low-order modulation in deployed networks.

Findings

Successful transmission of 975 Gb/s super-channel over 995 km.

Achieved spectral efficiency of 5.58 bit/s/Hz with OSNR=15.8 dB.

Long-term system reliability confirmed through measurements.

Abstract

Sub-Nyquist time frequency packing technique was demonstrated for the first time in a super channel field trial transmission over long-haul distances. The technique allows a limited spectral occupancy even with low order modulation formats. The transmission was successfully performed on a deployed Australian link between Sydney and Melbourne which included 995 km of uncompensated SMF with coexistent traffic. 40 and 100 Gb/s co-propagating channels were transmitted together with the super-channel in a 50 GHz ITU-T grid without additional penalty. The super-channel consisted of eight sub-channels with low-level modulation format, i.e. DP-QPSK, guaranteeing better OSNR robustness and reduced complexity with respect to higher order formats. At the receiver side, coherent detection was used together with iterative maximum-a-posteriori (MAP) detection and decoding. A 975 Gb/s DP-QPSK super-channel was successfully transmitted between Sydney and Melbourne within four 50GHz WSS channels (200 GHz). A maximum potential SE of 5.58 bit/s/Hz was achieved with an OSNR=15.8 dB, comparable to the OSNR of the installed 100 Gb/s channels. The system reliability was proven through long term measurements. In addition, by closing the link in a loop back configuration, a potential SE*d product of 9254 bit/s/Hz*km was achieved.