Assessment of Intra-channel Fiber Nonlinearity Compensation in 200 GBaud and Beyond Coherent Optical Transmission Systems

TL;DR

This paper evaluates intra-channel nonlinearity compensation in high-speed coherent optical systems, showing that even at 200 GBaud and beyond, significant gains are achievable despite challenges like polarization mode dispersion.

Contribution

It provides a comprehensive assessment of ideal and practical intra-channel nonlinearity compensation techniques at ultra-high symbol rates, including the impact of PMD and amplifier types.

Findings

Ideal IC-NLC gain decreases with higher symbol rates and PMD.

Practical IC-NLC gains increase with symbol rate, reaching up to 1.30 dB at 300 GBaud.

Significant nonlinearity compensation gains are possible at 200 GBaud and beyond.

Abstract

In this paper, we investigate and assess the performance of intra-channel nonlinearity compensation (IC-NLC) in long-haul coherent optical transmission systems with a symbol rate of 200 GBaud and beyond. We first evaluate the potential gain of ideal IC-NLC in 4 THz systems by estimating the proportion of self-channel interference (SCI) using the split-step Fourier method (SSFM) based simulation with either lumped amplification or distributed amplification. As the symbol rate increases to 300 GBaud, the SCI proportion exceeds 65%. On the other hand, the non-deterministic polarization mode dispersion (PMD) will impact the effectiveness of IC-NLC, especially for ultra-high symbol rate systems. Therefore, we investigate the power spectral density of the residual nonlinear noise after ideal IC-NLC in the presence of PMD. The results indicate that the gain of ideal digital backpropagation (IDBP) decreases by 3.85 dB in 300 GBaud erbium-doped fiber amplifier (EDFA)-amplified links with a PMD parameter of 0.05 ps/km1/2, and 5.09 dB in distributed Raman amplifier (DRA)-amplified links. Finally, we evaluate the potential gains of practical IC-NLC in C-band wavelength-division multiplexing (WDM) systems by employing the low-pass-filter assisted digital backpropagation (LDBP). As the symbol rate increases from 100 GBaud to 300 GBaud, the gain of 20-step-per-span (20-stps) LDBP increases from 0.53 dB to 0.87 dB for EDFA-amplified links, and from 0.89 dB to 1.30 dB for DRA-amplified links. Our quantitative results show that for 200 GBaud and beyond systems, there is a sizable gain to achieve by compensating for intra-channel nonlinearity even with a large non-deterministic PMD.