Abstract
In distributed Brillouin optical fiber sensor when the length of the perturbation to be detected is much smaller than the spatial resolution that is defined by the pulse width, the measured Brillouin gain spectrum (BGS) experiences two or multiple peaks. In this work, we propose and demonstrate a technique using differential pulse pair Brillouin optical time-domain analysis (DPP-BOTDA) based on double-peak BGS to enhance small-scale events detection capability, where two types of single mode fiber (main fiber and secondary fiber) with 116 MHz Brillouin frequency shift (BFS) difference have been used. We have realized detection of a 5-cm hot spot at the far end of 24-km single mode fiber by employing a 50-cm spatial resolution DPP-BOTDA with only 1GS/s sampling rate (corresponding to 10 cm/point). The BFS at the far end of 24-km sensing fiber has been measured with 0.54 MHz standard deviation which corresponds to a 0.5°C temperature accuracy. This technique is simple and cost effective because it is implemented using the similar experimental setup of the standard BOTDA, however, it should be noted that the consecutive small-scale events have to be separated by a minimum length corresponding to the spatial resolution defined by the pulse width difference.
Highlights
Optical fiber sensors have attracted much interest lately, due to their use in hazardous and hard to access environments [1,2,3]
For standard Brillouin optical time-domain analysis (BOTDA) sensor, the spatial resolution is determined by the pulse width which is limited by the acoustic phonons lifetime (~10 ns) [8] corresponding to 1 m, while the Brillouin gain spectrum (BGS) experiences broadening and amplitude reduction when the pulse width is smaller than 10ns [9]
Some field applications only need high spatial resolution at critical locations, while m-scale is enough for other parts
Summary
Optical fiber sensors have attracted much interest lately, due to their use in hazardous and hard to access environments [1,2,3]. A major technique that achieves long-range sensing with sub-meter spatial resolution is differential pulse width pair (DPP)-BOTDA [10, 11]. In 2012, Dong et al demonstrated 2-cm resolution over 2-km using differential pulse width pair (DPP) in transient domain [12] Another method to achieve cm-scale resolution is pre-excitation pulse technique [13]. The cm-scale perturbation (5 cm) was detected by using a small section of secondary fiber, while the spatial resolution was 50 cm for the rest of the sensing length This technique enables the detection of perturbations which correspond to one-tenth (1/10) of intrinsic spatial resolution given by the pulse width with a relatively low sampling rate.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
