Laser beam self-focusing in optical fiber controlled through FBG integration

Optical fibers are elements that are mainly used as a means to transmit light. In this paper, a fiber optic constituted by a core, a cladding and a Bragg grating in the core center has been studied. A laser beam with a Gaussian shape is let to propagate through the core of the fiber with an intensitydependent refractive index. In the center of the fiber, the refractive index will reach the highest value, focusing the beam. This property of the Gaussian beam to a specific intensity induces positive focusing is called self-focusing. A fiber Bragg grating is integrated inside the core of the fiber in order to control the self-focusing phenomenon. Five different materials are used for the grating for this purpose. An important relationship between the intensity of the beam inside the grating and, thus, the self-focusing and the material used is shown. The setup arrangement of the optical sensor is modeled through Comsol Multiphysics (Wave Optics Module), based on the FEM (Finite Element Method) solver.