Overcoming the Lead Fiber-Induced Limitation on Pulse Repetition Rate in Distributed Fiber Sensors

Abstract

Distributed fiber sensor (DFS)-based dynamic sensing has attracted increasing attention thanks to the growing demand in areas such as structural health monitoring and geophysical science. The maximum detectable frequency of DFSs depends on the maximum pulse repetition rate (MPRR), which is limited by the total length of the fiber under test (FUT). In some real-world applications, there is some distance between the interrogator and the monitoring site. Therefore, only a small part of the FUT acts as a sensing fiber (SF), while the other major part just acts as a lead fiber (LF), and the MPRR is limited by the LF and SF. Overcoming the LF-induced extra limitation on the MPRR is a practical problem for many DFS applications. In this paper, to the best of our knowledge, we propose a simple approach for overcoming the LF-induced extra limitation on the MPRR by dividing the DFS interrogator into two parts, for the first time. The proposed approach can be easily implemented for the real-world applicationsof DFSs whose LF is much longer than SF. It has been experimentally validated by using conventional phase-sensitive optical time domain reflectometry and Brillouin optical time domain analysis.

Quantitative Analysis of φ-OTDR Spatial Resolution Influenced by NLM Parameters

“…Additionally, the neural network can also significantly improve both MA and SR [23][24][25], but usually requires a lengthy data training process. Some methods based on special optical fiber and structure have been used to improve the SR and MA, but the cost of special fiber itself and installation is relatively high [26][27][28]. In short, the SRs obtained by the aforementioned filters are even several times better than that of NLM, which means that the signal broadening caused by NLM parameter can be very severe.…”

Self-Contained Reference Sensors to Reduce Nuisance Alarm Rate in φ-OTDR-Based Fence Intrusion Detection System

“…As one of the most important types of distributed optical fiber sensors, phase-sensitive optical time domain reflectometry (ϕ-OTDR) has attracted considerable attention in the past two decades due to the high sensitivity of monitoring vibration based on single-mode fibers (SMFs) over a long distance [1][2][3]. It has been widely used for fence intrusion detection.…”