基于超结构光纤光栅的自发布里渊散射检测系统设计与实现

为解决光纤背向散射信号中自发布里渊散射信号提取困难的问题,针对自发布里渊散射信号的频谱特点,设计并制作了一种双峰、波长可调结构的超结构光纤光栅滤波器。该滤波器具有滤波抑制比高、滚降特性好、线宽窄、中心波长可调、插损低、稳定性高等特点。通过两级超结构光纤光栅的级联,对瑞利散射信号的抑制达到约30 dB,可以把自发布里渊散射信号的2个峰同时提取出来。在此基础上,搭建了基于布里渊散射技术的全分布式光纤传感实验系统,对长度约为32 km的传感光纤进行了实验测量,在对被测光纤上长度为130、150 m的两段光纤分别施加1200μ,ε温度变化20°C时,系统较清楚地显示出应力、温度对被测光纤的作用效果。测量结果表明,该系统可以实现光纤温度及应力的变化监测。

Designing & realization of spontaneous Brillouin scattering detectingsystem based on super-structure fiber bragg grating

T o solve the problems in ex t ract ing spontaneous Brillouin scat ter ing signals from backscatteringsig nals in f iber , based on the spect rum characterist ics spo ntaneous Brillouin scat tering sig nals, a doublepeakw aveleng th-variable super -st ructure FBG filter w as desig ned and made. T he filter w as featured w ithhig h suppr ession ratio , ex cellent roll-of f , narrow line-w idth, tunable center w avelength, low inser tionloss and stability . T hrough the 2-level super-st ructure FBG cascade, inhibitio n of the Ray leig h scatteringsig nal r eached 30 dB, and the double peaks of the spontaneo us Br illouin scat tering signals could be obtainedat the same t ime. On such basis, the all-dist ributed o pt ical f iber sensing ex perimental system basedon Brillouin scat tering technique w as init iated to conduct measurement s on the sensing opt ical f iber of 32km long . Applied 1200 LE, w hen the temperatur e changes reached 20 °C on the tw o sect ions of the testedfiber w hose length w er e 130 m and 150 m respect iv ely , the system dist inct ly show ed the effect s on thetested fiber pieces by the str ain and the temperatur e. T he test ing result pr oves that the system can be usedto monitor the variat io n in opt ical fiber temperatures and st rains