# Twisted Fiber Bragg Gratings as a Polarization-Insensitive Element

## TL;DR

This paper introduces a new method to create polarization-insensitive Bragg gratings by twisting optical fibers during fabrication.

## Contribution

The novel approach uses pre-twisted fibers with femtosecond lasers to significantly reduce polarization dependence in Bragg gratings.

## Key findings

- Twisted gratings showed a tenfold reduction in polarization dependence of reflection levels.
- Bragg wavelength polarization dependence decreased threefold compared to straight gratings.
- The method is suitable for high-precision Bragg sensor production.

## Abstract

This work proposes an original method for fabricating Bragg gratings using the point-by-point technique with femtosecond laser radiation, which minimizes the polarization dependence of the gratings’ optical response. The method is based on inscribing the Bragg structure in a pre-twisted optical fiber. The results of the experiments demonstrated a radical reduction in the polarization dependence of such gratings. The polarization dependence of the reflection level and Bragg wavelength in the twisted grating decreased by at least an order of magnitude and by three times, respectively, compared to the straight FBG. The results can be used in the production of high-precision Bragg sensors.