Fiber optic sensors can measure a large range of physical, chemical and environmental variables such as temperature, pressure, shape, position, chemical concentration, moisture, etc. Fiber optic sensors provide measurements in applications where the conventional electrical based sensors cannot be used, due to measurement requirements such as extreme temperature, small size, high sensor count, or high electromagnetic energy or radiation environments. In this paper, we propose a study of an optical sensor based on a Fiber Bragg Grating (FBG) setup arrangement using COMSOL Multiphysics. The effect of environmental parameters on the composite material machine part is observed by the modification of the length (L) of the Fabry-Perot interferometer formed by two Bragg grating mirrors. This variation can be studied by a transmission spectroscopy measurement. The developed COMSOL Multiphysics sensor model takes into account the interaction of Fiber Bragg Grating (FBG) with composite material.