Fiber Nonlinearity Compensation by Digital Backpropagation of an Entire 1.2-Tb/s Superchannel Using a Full-Field Spectrally-Sliced Receiver

Digital Back-Propagation for High Spectral Efficiency Terabit/s Superchannels

“…We found that the optimal values are different for different digital bandwidths and, consistent with [2], varying for different distances and launch powers. Therefore, we selected optimal values for which the longest transmission distance (reach) was achieved at the BER threshold of 10 -2 (Q 2 =7.33 dB), which represents a conservative threshold for 20% or higher redundancy soft-decision FEC schemes.…”

“…The digital bandwidth was varied from 2 samples per symbol up to 5 samples per symbol (full bandwidth DBP) and BER is evaluated for the central sub- channel to characterize the DBP benefit and a result of a trade-off between the in-band noise and inter-channel nonlinear distortion. In a real system where the bandwidth of each "stitched" receiver roughly fit the bandwidth of a single sub-channel, such an implementation would correspond to stitching by "clusters" of sub-channels before applying DBP, differently from [2] where the superchannel bandwidth is entirely digitally reconstructed. It is a reasonable to predict that the former technique might be less impaired from the non-ideal phase matching between several sub-channels.…”

“…After detecting the entire superchannel bandwidth it is possible to operate DBP at different digital bandwidths in order to include one or more sub-channels. Recently it has been shown that there are benefits from back-propagating the entire superchannel (full-bandwidth DBP) compared to doing it over a single sub-channel basis [2,3] because of the cancelation of inter-channel nonlinear effects. Nevertheless it is well understood that DBP benefit can be limited by different non-ideal scenarios such as the amount of back-propagated noise at the receiver, polarization mode dispersion (PMD) [4] or limited sampling rate [1].…”

On the performance of multichannel digital backpropagation in high-capacity long-haul optical transmission

“…To assess the effectiveness of multichannel DBP under different operating conditions we simulated a super-channel made up of 5 phase-locked 32 Gbaud channels with 33 GHz spacing, delivering a 1.2 Tbit/s raw transmission rate as in [24] and consistent with the experimental setup in [23]. However, in contrast to [24] where the aim was to explain previously reported experimental results [23], in this work we consider a system with an ideal transmitter and receiver yielding no back-to-back implementation penalty.…”

“…When multichannel DBP has been applied in experiments, the reported benefits have proved relatively low, typically less than 1 dB in Q 2 factor for long-haul systems [21][22][23]. The factors which contribute to the discrepancy between the theoretically achievable DBP benefit and the gains experimentally realized have not yet been well identified or explained.…”