Single-Mode Input Fiber Combined with Multimode Sensing Fiber Used in Brillouin Optical Time-Domain Reflectometry

Conventional single-mode fiber (SMF) Brillouin optical time-domain reflectometry (BOTDR) suffers from a low signal-to-noise ratio (SNR) and severe sensing reliability due to the influence of stimulated scattering threshold bend loss. In this study, simple low-cost distributed structure, with input alignment fusion 50 ?m diameter graded index multimode fiber, is designed, SNR characteristic investigated. Through theoretical derivation experimental verification, higher excellent bending resistance are realized in BOTDR. The experimentally measured improvements proposed structure over SMF at beginning end 5 km 2.5 dB 1.3 dB, respectively. minimum radius 2.25 mm, which much better than that SMFs. bidirectional losses between by experiment system 0.106 1.35 temperature-sensing characteristics self-built frequency-shift local heterodyne BOTDR sensor, temperature sensitivity accuracy 0.946 MHz/? 1 ?, design provides reference for high has great potential structural safety health monitoring infrastructures.