Study Of Stimulated Raman Scattering In Optical Fiber Gratings

With the development of theoretic research and manufacturing technology of optical fiber grating,it has been taken as a good solution to many key optical communication devices (such as filter, light source, optical amplifier and so on). Not only the linear effects of fiber gratings are widely used, the nonlinear effects also have a great potential to applications.The characteristics of optical fiber gratings and Stimulated Raman Scattering(SRS) are firstly introduced, and characteristics of fiber gratings are analyzed through its linearity and nonlinearity. Then the diffraction in fiber Bragg grating is analyzed, and nonlinear coupled-mode equations are deduced from Maxwell equations and Helmholtz equations, and numerically solved through implicit Runge-Kutta method.Optical fiber gratings'analyzing programme has also been written in Matlab using implicit Runge-Kutta method so as to analyze the nonlinearity of fiber gratings. Firstly SRS in fiber gratings for the continuous pulse input is analyzed, then SRS for different intensity of Guass pulse input and different intensity of Guass pump input is compared, nonlinear soliton's characteristics of fiber gratings is also analyzed. The results show that the width of pulse is expanded and the amplitude is attenuated for the low intensity pulse input; the width, amplitude, and speed of the pulse remain the same for the high intensity pulse input,thus nonlinear gap soliton is formed; the width of the pulse is compressed for very high intensity pulse input, but a linear chirp which changes with the propagation distance is produced at the same time; the width of the weak pulse is compressed for the input of low intensity pulse with its wavelength situated in negative dispersion area and high intensity pump pulse with its wavelength situated in positive dispersion area. Finally, the results are summarized.