## Spectrally Efficient Long-Haul Optical Networking Using 112-Gb/s Polarization-Multiplexed 16-QAM

Journal of Lightwave Technology, Vol. 28, Issue 4, pp. 547-556 (2010)

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### Abstract

We discuss the generation, wavelength-division-multiplexed (WDM) long-haul transmission, and coherent detection of 112-Gb/s polarization-division-multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM) at a line rate of 14 Gbaud and spectral efficiencies beyond 4 b/s/Hz. We describe the (off-line) digital signal processing and blind filter adaptation algorithms used in our intradyne receiver and characterize its performance using both simulated and measured 16-QAM waveforms. We measure a required optical signal-to-noise ratio of 20.2 dB (0.1-nm reference bandwidth; $10^{-3}$ bit-error ratio), 3.2-dB off the theoretical limit. We study the effects of finite analog-to-digital converter resolution, laser frequency offset, laser phase noise, and narrowband optical filtering. Our experiments on a 25-GHz WDM grid (4.1-b/s/Hz spectral efficiency) reveal a 1-dB penalty after 7 passes though reconfigurable optical add/drop multiplexers (ROADMs) and an achievable transmission reach of 1022 km of uncompensated standard single-mode fiber. At a spectral efficiency of 6.2 b/s/Hz (16.67-GHz WDM channel spacing) a transmission reach of 630 km is attained.

© 2010 IEEE

**Citation**

P. J. Winzer, A. H. Gnauck, C. R. Doerr, M. Magarini, and L. L. Buhl, "Spectrally Efficient Long-Haul Optical Networking Using 112-Gb/s Polarization-Multiplexed 16-QAM," J. Lightwave Technol. **28**, 547-556 (2010)

http://www.opticsinfobase.org/jlt/abstract.cfm?URI=jlt-28-4-547

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