The use of Fiber Bragg Grating (FBG) as Fabry – Perot filter has been successfully developed for visible light and ultraviolet spectra. The characteristic of FBG is analyzed by using computational model with Transfer Matrix Method by order 2 with the coupled mode theory. The reflectivity, length of grating and bandwidth are parameters to determine the performance of FGB with laser source of 1 mW for 250 – 350 nm, ultraviolet and 380 – 780 nm, visible light. The simulation is also carried out by various grating from 0.5 cm – 9.5 cm with increment step of 1 cm. The simulation result showed that there is the filter discrepancy for maximum peak. This design of FGB can be used as a filter. Only selected wavelength is allowed to transmit the signal until the end of the optical fiber.