Probabilistic 16-QAM Shaping in WDM Systems

This work proposes a probabilistic shaping scheme for optical WDM systems, where nonlinear interference noise depends on the input optical signal power distribution. With 16-QAM, a white Gaussian channel analysis shows that the shaped constellation is able to achieve a reach improvement of up to 7%, while split-step Fourier method simulations suggest that even higher gains are possible in practice. An example system is developed for a transmission distance around 3280 km. A constellation mapping and a low-density parity-check code are developed for this regime to show a reach improvement of 7.1%. These shaping schemes can also be extended to 64-QAM, where a reach improvement of over 10% is expected.