# Nonlinear Depolarization of Light in Optical Communication Fiber

## TL;DR

This paper experimentally observes a nonlinear depolarization phenomenon in optical fibers, revealing ultra-fast polarization fluctuations caused by nonlinear interactions, and questions the validity of the Manakov equation in noisy conditions.

## Contribution

It introduces a novel experimental observation of nonlinear depolarization in optical fibers and provides a phenomenological and theoretical framework to understand this phenomenon.

## Key findings

- Depolarization leads to ultra-fast polarization fluctuations.
- The Manakov equation's applicability is questioned in noisy environments.
- The phenomenon offers insights into discrepancies between simulations and experiments.

## Abstract

We report the experimental observation of a novel transmission phenomenon in optical long-haul communication systems. Un-polarized ASE depolarizes via nonlinear fiber interactions a cw laser light during their co-propagation which leads to small but measurable ultra-fast polarization state fluctuations at the fiber output. We provide a phenomenological approach and a theory that qualitatively corroborates our experimental results. One of our major findings suggests that the applicability of the often used Manakov equation needs to be scrutinized for highly accurate studies of nonlinear polarization state evolutions in noisy environments. The described phenomenon leads to a qualitatively different microscopic understanding of nonlinear light propagation in fiber and can contribute towards an explanation for todays commonly perceived gap between simulated and experimentally obtained system performance in optical data transmission.

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Source: https://tomesphere.com/paper/1902.05168