Detection Of Water Pipeline Leakage Based On Distributed Optical Fiber Sensing

Water,the source of life,is becoming more and more scarce,especially in our country.Pipeline network is a major way of transport for tap water.A significant amount of water is lost due to leakage from pipelines every year in our country,and that is far higher than the international level.The leaks not only seriously affect people's daily life and normal industrial or agricultural operations,but also cause enormous resource waste and economic loss.Therefore,effective monitoring of water distribution pipes is very important.In recent years,optical fiber sensors have attracted much attention due to their unique advantages such as easy installation,long-term stability,resistance of electromagnetic interference and corrosion.In this paper,the feasibility of monitoring water pipeline leak with the distributed temperature sensing(DTS)technique based on Raman optical time domain reflectometer(OTDR)is studied.This method is based on the temperature effect of the Raman scattering.The Anti-Stokes of Raman scattering is sensitive to temperature,and can perceive temperature information along the optical fiber.This temperature information can be demodulated by using the Stokes as reference signal.The pipelines can be extensively detected in real time by using distributed optical fiber sensing technique.Suitable components are chosen according to the practical situation to comprise a DTS system with spatial resolution of 1m and temperature resolution of 1?.Based on the cumulative average method,the signal to noise ratio is improved by 180 times.The simulative tests have demonstrated that this DTS system can detect and locate the leakage when the temperature difference between the water and the surrounding is no less than about 1?.The water leakage spreading range is reflected to some extent,and when the leaks are spaced by 1m or more,they can be distinguished successfully.When the length of the leakage water contacted with the sensing optical fiber increasing from 1m to 2 m,the wave packet is greater both in the amplitude and the width.A pipeline leakage alarm system is also developed based on the change in the output waveform.With a certain average pulse power,the threshold temperature variation which can be detected by the alarm system will be higher at longer distance;while in the same position,a lower threshold temperature can be achieved with increased pulse power.In addition,when the length of the sensing optical fiber which is contacted with the leakage water is longer,the threshold temperature variation of the alarm system can also be reduced.