We propose an interesting result of the trapped multiphotons distribution within a fiber Bragg's grating. The multitrapped photons are confined by the potential well, where the motion of photons in a fiber Bragg's grating is affected by the external perturbations, which they are defined as a series of nonlinear parametric in terms of potential energy. This investigation is modeled by using the nonlinear coupled mode equations and under Bragg's resonance condition, where the initial frequency of the light, ω 0 is the same value as the Bragg's frequency, ω B . Results obtained have shown that the higher perturbation series represents the potential well is much differed from the equilibrium situation. In applications, the external perturbations on the fiber grating can cause the trapped photons instability, which introduces the escaped photons from the potential well being detected and observed. The potential of applications for quantum encoding device can be performed, which is analyzed and discussed in details.