Study On The Mechanism Of Mode Maintenance Brillouin Amplification In Multi-mode Optical Fibers

The feature of transmitting multiple spatial mode in Multi-mode fiber havebroad application prospects in many areas, such as local area networkcommunication, the use of multiple-input-multi-out mode groups divisionmultiplexing system can greatly improve the existing multimode fibercommunication capacity. If we can amplify the spatial transmission mode withoutchanging the mode distribution, it will provide strong support on such technology.This paper intends to adopt Brillouin amplification method to explore thefeasibility and optimal parameter conditions of mode maintains Brillouinamplification with different transmitted modes of seeds.First considering a variety of theoretical models and basic parameters thatmay involve in Brillouin amplification mode maintains technology. Based oncoupled wave equations in stimulated Brillouin scattering, combined with theguided mode field distribution in multimode fiber with different refractive index,we established a multi-mode fiber transient stimulated Brillouin scattering model.Then discretize this model and process the numerical modeling andsimulation. Coupling strength coefficient of stimulated Brillouin scatteringbetween each mode in multimode fiber and the influence of Brillouin gain withdifferent refractive index distribution is obtained by numerical calculation. Theeffects of parameters in Brillouin amplification process such as the refractiveindex distribution of the multimode fiber, delay distance between the seed lightwith the pump light, peak power and pulse width of the pump light, peak powerand the mode field distribution of the seed light on Brillouin extraction efficiencyand mode maintains characteristics is detailed discussed.The experiment of Brillouin amplification mode remains is carried out with62.5μm and105μm core diameter GI multimode fiber. The wavelength of thelight sourse is1.064μm, full width at half maximum of the pulse is8ns. Inject aseed light with3μJ pulse energy into the multimode fiber, then carefully adjustthe delay distance between the pumping light with the seed light and the energyof the pumping light, the experiments obtains a amplification light that canobvious maintain the field distribution of the seed light...