The monitoring of concrete cracks with distributed optical fiber sensors (DOFS) is very attractive for large concrete structures, e.g. dams and bridges. Its distributed measurement capability is particular advantage for application to detect the crack in dams since it arises at random specially. A new type of the DOFS using common communication optical fibers is laid in concrete crossing obliquely with the potential crack expected. Cracking induces two local microbends and cause attenuation of returning Rayleigh scattering. Its distributed sensing is based on optical time domain reflectometry (OTDR) .Yele's Dam's field tests show it can not only detect crack width and shear displacement with high resolution (0.02mm) , large dynamic range (4.8mm) but also localized them with high precision of localization (0.2m). A typical proposal scheme of application of the DOFS into the Yele Dam, Sichuan Province of China, is presented. The results afford a sound technique-basis for developing the practical crack sensing system of distributed optic-fiber.%分布式光纤传感技术对大型混凝固结构,如大坝与桥梁,进行裂缝监测意义重大,其分布式检测能力对具有强随机性的大坝裂缝监测效果更显著.一种新型分布式光纤传感器埋入混凝土并与预期裂缝相交一定斜角,当裂缝出现引起光纤局部微弯,并诱发瑞利散射光产生衰减,用光时域反射技术实现分布式检测.将该种传感器用于四川石棉冶勒大坝裂缝监测,结果表明:该光纤传感器不仅对裂缝宽度、位移具有高分辨率(0.02 mm)、大动态范围(4.8 mm),而且有较高的定位分辨率(0.2 m),为发展该类分布式光纤传感监测系统提供了较好的技术基础.
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