# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1812.03556