BOTDR的已敷设传感光纤温度和应变区分测量方法

为了解决已敷设传感光纤中布里渊谱峰功率初值难以获取,基于频移和功率双参量的温度和应变区分测量误差大等问题,提出了解决方法。通过标定实验确定布里渊频移和相对谱峰功率的温度和应变系数、频移初始值;根据布里渊散射功率特性方程,通过试探法,利用已敷设光路中温度和应变已知的参考光纤确定方程系数,建立了谱峰功率初始值;利用归一化方法克服了传感系统中乘性噪声导致的测量误差;利用谱宽变化消除了温度和应变突变点处的谱峰功率异常峰值;最后,根据光纤复合海底电缆的现场情况建立了模拟光路,并进行了温度和应变测量实验。结果表明,在5.6 km处可实现4.3℃和110 的测量精度,可实现已敷设传感光纤整条光路上的温度和应变区分测量,为工程应用提供了理论和实验依据。

Distinguish measurement of temperature and strain of laid sensing optical fibers based on BOTDR

In order to solve the problems that the initial value of Brillouin peak power in laid sensing optical fibers is hard to be obtained and the measurement error of temperature and strain is large based on Brillouin frequency shift and peak power, the method of distinguish measurement of temperature and strain is proposed. The Brillouin frequency shift and relative peak power coefficients of temperature and strain, as well as initial Brillouin frequency shift, were obtained by calibration experiment. The coefficients in Brillouin power equation were obtained by heuristic method according to the reference fiber in known temperature and strain. Then the initial Brillouin power distribution along the laid fiber was obtained. The measurement error caused by multiplicative noises in sensing system was conquered by normalization. The spikes in the Brillouin peak power profiles at positions of changed temperature or strain were eliminated by using spectral width change. The simulated optical path of optical fiber composite submarine power cable in engineering field was established. The measurement experiment of temperature and strain was performed. The results indicate that the measurement accuracy are 4.3℃ and 110 at 5.6 km. The distinguish measurement of temperature and strain for laid sensing fiber can be realized. The method can provide theoretical and experimental basis for engineering applications.