Introducing the phase distribution of fiber grating and taking into consideration the back-and-forth phase shift of the light in the external cavity

this paper analyzes the influence of temperature and the length of the external cavity on the Fiber Bragg Grating（FBG）-External Cavity semiconductor Lasers（ECL） mode by using four-order Runge-Kutta method.The numerical simulation results show that the number of the FBG-ECL mode increases and the intermode spacing decreases with the increase of temperature and external cavity length and the influence of the changes of the external cavity length on the hopping of the FBG-ECL mode becomes obvious.