Study On Stimulated Brillouin Scattering In Fiber Amplifier

Fiber lasers and amplifiers have attracted much attention due to their manyadvantages, including excellent beam quality, high efficiency, robust reliability, totalcompactness and good heat management. These features demonstrate great potential inapplication of telecommunications, industry, and medicine et al. But in fiber amplifiers,some nonlinear processes such as stimulated brillouin scattering (SBS), stimulatedraman scattering (SRS) and self phase modulation (SPM) et al. are easily induced, dueto the high power, small core mode cross section and long interaction distance.Generally the SBS process has the lowest threshold than other nonlinear processes. So itimportant to study the physical process and the suppression method of SBS in fiberamplifiers.The purpose of this article is to study the SBS process in fiber amplifiers, whichwill enhance the comprehension and improves the understanding of the physicalmechanics of this kind of nonlinear process and explores the suppression method ofSBS in fiber amplifiers. The theoretical and experimental studies are done with Yb - 3+doped double-clad fiber amplifiers, the main work are as flowing:1. Based on the structure of Yb3+-doped double-clad fiber and ytterbium ion leveltheory, the model of double-clad fiber amplifier is set up, the equations describing thepower transport process are deduced and numerically solved.2. According to the model, the numerical simulation is carried out. The influencesof different parameters are analyzed, including signal power, fiber length, pumpschemes, pump power, doping concentration and convective coefficient.3. The influence of delivery fiber on SBS process in fiber amplifier is studied. Theinfluence factors mainly include the length and geometrical structure of the deliveryfiber.4. The experiments of SBS process in fiber amplifier are done, the experimentalresults are discussed and the correctness of simulation results is verified.