  In this Letter we analyze the benefit of digital compensation of fiber
nonlinearity, where the digital signal processing is divided between the
transmitter and receiver. The application of the Gaussian noise model indicates
that, where there are two or more spans, it is always beneficial to split the
nonlinearity compensation. The theory is verified via numerical simulations,
investigating transmission of single channel 50 GBd polarization division
multiplexed 256-ary quadrature amplitude modulation over 100 km standard single
mode fiber spans, using lumped amplification. For this case, the additional
increase in mutual information achieved over transmitter- or receiver-side
nonlinearity compensation is approximately 1 bit for distances greater than
2000 km. Further, it is shown, theoretically, that the SNR gain for long
distances and high bandwidth transmission is 1.5 dB versus transmitter- or
receiver-based nonlinearity compensation.
