Page - 1425 - in Book of Full Papers - Symposium Hydro Engineering

In 1987, Sensa firstly released a distributed optical fiber temperature sensing system (DTS) based on backward Raman scattering. After that, the distributed optical fiber temperature measurement techniques have been commercialized by increasing companies. In the domestic cases, the earliest optical fiber temperature sensing techniques were actually applied to the project of Shimen Dam by Tsinghua University and Munich University of Technology. Zhang Zaixuan[5] developed the FGC-Wl laser distributed Raman temperature sensing system in 1995. Afterwards, the FGC-W2 distributed optical fiber temperature sensing system[6] was further developed and its temperature resolution can reach 0.1 ℃. In 2002, Prof. Cai Desuo[7] introduced a DTS200-8-M2 distributed optical fiber temperature measurement system from Sensa and applied it to the 14th section of the left power house of the Three Gorges Dam. In 2007, Prof. Zhou Yihong[8] applied the distributed optical fiber temperature measurement techniques to Xiluodu Hydropower Station. In 2011, Prof. Zhang Zixuan successfully reduced the temperature drift of the optical fiber temperature measurement system[9]. The Wudongde dam located in the dry and hot valley is a concrete double- curvature arch dam with the foundation surface elevation of 718m, crest elevation of 988m and a maximum dam height of 270m. The temperature difference between morning and evening is large, moreover, the ground temperature is high and the evaporation is large. Therefore, it’s a big challenge to control the dam temperature. The low-heat cement used in Wudongde dam can improve the crack resistance of mass concrete due to its low heat of hydration and the post-concrete performance close to or over that of medium-heat Portland cement. However, the early strength development of low-heat cement concrete is slow and it is also the first time for the large-scale use of full-dam in China. It is hard to make sure the evolution of the true temperature field inside the low-heat mass concrete. Therefore, using the distributed optical fiber for concrete temperature monitoring is very significant. 2. DISTRIBUTED OPTICAL FIBER INTELLIGENT TEMPERATURE MONITORING SYSTEM 2.1. BASIC PRINCIPLE OF THE SYSTEM Optical fiber temperature measurement system is composed of the host computer of the DTS (Distributed Temperature System), data network, distributed optical fiber, human-computer interface and cloud platform. The host computer of the DTS is an optical instrument which measures the temperature through the optical fiber. The optical fiber is similar to a sensor that monitor the temperature. The host computer provides the operation interface and it can not only measure the temperature intermittently but also measure continuously in real time. Furthermore, it provides the interface of data file and real-time protocol of data exchange for networking. Data networks can use wired or wireless means. 1425