How to Increase the Achievable Information Rate by Per-Channel Dispersion Compensation

TL;DR

This paper demonstrates that per-channel dispersion compensation in fiber optic links enhances the achievable information rate by improving XPM mitigation, leveraging frequency correlation of distortions for better performance.

Contribution

It introduces the novel insight that per-channel dispersion-managed links enable more effective XPM compensation and higher AIR compared to non-dispersion-managed links.

Findings

Per-channel dispersion compensation increases XPM frequency correlation.

CDM links outperform NDM links when XPM is compensated.

DM links have the lowest AIR due to stronger XPM effects.

Abstract

Deploying periodic inline chromatic dispersion compensation enables reducing the complexity of the digital back propagation (DBP) algorithm. However, compared with nondispersion-managed (NDM) links, dispersion-managed (DM) ones suffer a stronger cross-phase modulation (XPM). Utilizing per-channel dispersion-managed (CDM) links (e.g., using fiber Bragg grating) allows for a complexity reduction of DBP, while abating XPM compared to DM links. In this paper, we show for the first time that CDM links enable also a more effective XPM compensation compared to NDM ones, allowing a higher achievable information rate (AIR). This is explained by resorting to the frequency-resolved logarithmic perturbation model and showing that per-channel dispersion compensation increases the frequency correlation of the distortions induced by XPM over the channel bandwidth, making them more similar to a conventional phase noise. We compare the performance (in terms of the AIR) of a DM, an NDM, and a CDM link, considering two types of mismatched receivers: one neglects the XPM phase distortion and the other compensates for it. With the former, the CDM link is inferior to the NDM one due to an increased in-band signal--noise interaction. However, with the latter, a higher AIR is obtained with the CDM link than with the NDM one owing to a higher XPM frequency correlation. The DM link has the lowest AIR for both receivers because of a stronger XPM.