Theoretical study of optical fiber Raman polarizers with counterpropagating beams

TL;DR

This paper develops a comprehensive theoretical model for optical fiber Raman polarizers with counterpropagating beams, describing their polarization and gain characteristics in various regimes, including undepleted and depleted cases.

Contribution

It introduces a detailed, computer-friendly theory for Raman polarizers in randomly birefringent fibers, applicable to multiple propagation configurations and regimes.

Findings

The theory accurately predicts the degree of polarization and gain in Raman polarizers.

It extends previous models to include counterpropagating beams and depleted regimes.

The model is versatile and applicable to practical fiber optic systems.

Abstract

The theory of two counter-propagating polarized beams interacting in a randomly birefringent fiber via the Kerr and Raman effects is developed and applied to the quantitative description of Raman polarizers in the undepleted regime. Here Raman polarizers, first reported by Martinelli et. al. [Opt. Express. 17, 947 (2009)], are understood as Raman amplifiers operating in the regime in which an initially weak unpolarized beam is converted into an amplified fully polarized beam towards the fiber output. Three parameters are selected for the characterization of a Raman polarizer: the degree of polarization of the outcoming beam, its state of polarization, and its gain. All of these parameters represent quantities that are averaged over all random polarization states of the initially unpolarized signal beam. The presented theory is computer friendly and applicable to virtually all practically relevant situations, including the case of co-propagating beams, and in particular to the undepleted as well as the depleted regimes of the Raman polarizer.