Research On Stimulated Brillouin Scattering Characteristics In Few-mode Fiber Based On W-S Additive Model

In recent years,with the rapid development of China's information technology,Optical fiber sensing technology is used in many fields,promoting the development of many industries,the development prospects are very expansive.Stimulated Brillouin Scattering(SBS)is a very important nonlinear effect in optical fibers.It has expansive application value in optical fiber sensor,optical fiber lasers and so on.Now the research on SBS is focused on suppressing the SBS effect to reduce its effects on systems and achieving distributed optical fiber sensing by using SBS effect.In this paper,the Brillouin scattering properties as well as temperature and strain sensing properties in few-mode fibers which consist of different kinds of doped materials are investigated based on the W-S additivity algorithm for characterizing the optical fiber material properties.The main research elements are as follows.(1)The W-S additivity model which expresses optical fiber material properties is constructed and validated.The acoustic-optic effective area formula and Brillouin gain spectrum expression between different optical mode pairs and stimulated acoustic modes are obtained by solving the field distributions of the optical and acoustic modes.Furthermore,the formula of Brillouin frequency shift varying with temperature and strain in optical fiber is derived in detail.(2)Non-thermal sensing applications based on SBS properties are studied.The brillouin gain spectrum of a La₂O₃-Al₂O₃-SiO₂ fiber(SAL)is analysed and the influence of the SAL fiber parameters(concentration ratio of the doped materials and radius)on the sensing characteristics is also investigated by means of a W-S additivity model.In addition,The conclusion SBS can be suppressed by using the characteristics of doped materials is confirmed based on SAL fiber.Finally,a SAL-a fiber with better performance is proposed,which satisfies the non-thermal sensing conditions with a strain sensitivity enhancement.(3)The Brillouin scattering properties and the application of simultaneous temperature and strain sensing for M-FMF with five different kinds of doped materials(GeO₂?BaO?P₂O₅?SrO?La₂O₃)are studied.The findings show that theLP₀₁-LP₀₁ mode pairs andLP₀₁-LP₁₁ mode pairs in M-FMF with five different kinds of doped materials can all realize simultaneous temperature and strain sensing.When the concentration ratio of the doped materials is the same,the temperature and strain sensing performance of GeO₂-doped M-FMF is the best.