Temperature and Strain Discrimination in BOTDA Fiber Sensor by Utilizing Dispersion Compensating Fiber

Standard single mode fiber that normally used in Brillouin optical time domain analysis fiber sensors typically has only one Brilllouin gain peak (BGP), and its central frequency [i.e., Brillouin frequency shift (BFS)] can be affected by both temperature and strain, which gives rise to temperature and strain cross sensitivity. In this paper, we propose a new method to realize temperature and strain discrimination, for the first time to the best of our knowledge, by using commercial single mode dispersion compensating fiber (DCF) that has two BGPs located around 9.536 and 10.052 GHz, respectively. The two peaks have different temperature coefficients but nearly the same strain coefficients, which permits simultaneous temperature and strain sensing by combing the BFSs obtained from the two BGPs. The biggest advantage of the DCF is that the frequency space between its two BGPs is >100 MHz wider than some other fibers, ensuring much wider temperature and strain sensing range. In a proof of concept experiment, temperature and strain are fully discriminated with a temperature resolution of ~2.6 °C and a strain resolution of ~64.6 με at the end of a 1-km sensing fiber with 2-m spatial resolution.