PDL and DGD Reduction in Bragg Gratings Using Twisted Fibers for the Inscription

We report the possibility to reduce the polarization-dependent loss (PDL) and the differential group delay (DGD) in fiber Bragg gratings (FBGs) by inducing polarization-mode coupling (PMC). To induce the PMC, the fiber is twisted before the inscription and then relaxed once the FBG is written. The theoretical concept as well as the simulation method used to study FBGs exhibiting PMC is detailed. The obtained results point out a significant decrease of the gratings' PDL and DGD values. In addition, experimental results, in good agreement with the theory, demonstrate the possibility to implement this method in practice.