Twisted Fiber Bragg Gratings as a Polarization-Insensitive Element

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.