Spectrally Efficient Long-Haul WDM Transmission using 224-Gb/s Polarization-Multiplexed 16-QAM
15 February 2011
We discuss the generation, wavelength-divisionmultiplexed (WDM) long-haul transmission, and coherent detection of 224-Gb/s polarization-division-multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM) at a line rate of 28 Gbaud. We measure a required optical signal-to-noise ratio of 23.4 dB (0.1-nm reference bandwidth; 10-3 bit-error ratio), 3.4dB off the theoretical limit. Using ultra-large-area fiber, we achieve 2,000-km single-channel transmission. We also demonstrate 1,200-km WDM transmission on a 50-GHz grid (4.1-b/s/Hz spectral efficiency), including three passes through a wavelength-selective switch.