Investigation of Long Period Fiber Gratings Sensitivity to Liquid Crystal External Medium

Abstract

In this work, we study the response of Long Period Fiber Gratings (LPG) to an external Nematic Liquid Crystal medium. By a coupling between the fundamental mode of the core and the cladding modes of the fiber, losses occure at different wavelengths. The spectral position and the intensity of those losses depending on the index of the external medium, one can expect that different orientations of the NLC will induce a modification of the response of LPG. To check this assumption, we have realised two types of experiments: In a first time, we have studied the response of LPG to different treatments of the fiber. In particular, we present for the first time a method to obtain a planar alignment directly on the fiber. It will then be demonstrated that the response of LPG can be modified by Fredericksz reorientation of NLC, creating new opportunities in telecommunications networks.