Distributed Optical Fiber Sensing Based On Brillouin Scattering Based Research

In China, Internet of Things is developing rapidly, the underlying structure ofwhich is the sensor network. Fiber is used as both the sensing element and thetransmission medium in distributed optical-fiber sensing techniques. Distributedoptical-fiber sensing not only well suited to realize long-distance sensing, but also tomonitor a large2D area or ever an entire3D structure, which makes it the keytechnology of health monitoring. Since it is sensitive to both temperature and strain in along distance besides the high sensing accuracy, distributed optical-fiber sensingtechnology based on Brillouin scattering effect is becoming one of the hot spots incurrent research field.The scheme of a specific Brillouin Optical Time Domain Reflectometry system isbeen presented, which enables both temperature and strain sensing. The test system hasalso been built and analyzed by experiment. After introducing the principle ofdistributed optical-fiber sensing utilizing Brillouin scattering effect, a few ways todetect Brillouin scattering signal have been summarized. Then a scheme of a specificBrillouin Optical Time Domain Reflectometry system is presented through a lot ofanalysis of the proposed performance indexes of the system. The choice of importantparameters of the key devices in this system has also been analyzed in detail. A newscheme of optical pulse modulator has been proposed which is small, low cost andintegrated, not only has high extinction ratio, but also enable to adjust the pulse width,especially adapts to Brillouin Optical Time Domain Reflectometry system. Scramblerwas used to eliminate polarization sensitivity of the coherent detection when theBrillouin scattering signal was detected. What’s more, some experiments wereperformed to analyze how the stimulated Brillouin threshold can be affected by differentwidth of optical pulse or sensing distance and how the coherent detection performancecan be affected by different types of photo detector. The feasibility of temperature andstrain sensing has been verified by experiments. At last, the proposed Brillouin opticaltime-domain reflectometry test system was made into a module which played animportant role in the promotion of the practical use of the Brillouin Optical Time Domain Reflectometry.