Design of a Weak Fiber Bragg Grating Acoustic Sensing System for Pipeline Leakage Monitoring in a Nuclear Environment

We propose a design method of a weak fiber Bragg grating (FBG) array, in which the reflectivity of the FBG increases along the fiber, and this increase is limited by the dynamic range of the distributed optical fiber sensing (DOFS) system. For a DOFS system, this design method can not only well compensate for the impact of fiber loss, within a certain range and caused by radiation, on the deterioration of the system performance, but also can reduce the requirements for the dynamic range of the system in nuclear environments. Based on this design method, we propose a short-distance acoustic detection system based on broadband ultraweak FBGs assisted phase-sensitive optical time domain reflectometry (Phi-OTDR), and assess the system's ability to detect pipeline leakages. This work not only provides guidance for the design of FBG sensing systems but also provides a new promising scheme for the application of DOFS system in nuclear environments.