Differential Reflectometry of Fiber Bragg Gratings
A reflectometric approach is proposed for interrogation of multiple fiber Bragg grating (FBG) sensors recorded in a single fiber optic line, based on the differential registration FBGs’ response to a short probing laser pulse using conventional OTDR. A special optical layout has been developed allowing transformation of FBG’s spectrally modulated signals into intensity modulated signals and at the same time eliminating the susceptibility of the system to light power fluctuations. Threshold sensitivity of the method amounted to ~50 μstrain within the measurement range of ~4000 μstrain. The maximum number of FBGs interrogated by the proposed technique is estimated at several hundred, which by far surpasses the requirements of most practical applications. Due to its simplicity, efficiency and usage of conventional OTDR equipment the proposed FBG interrogation technique can find a wide range of applications, in particular in structural health monitoring.
Yuri Chugui, Yongsheng Gao, Kuang-Chao Fan, Roald Taymanov and Ksenia Sapozhnikova
Y. N. Kulchin et al., "Differential Reflectometry of Fiber Bragg Gratings", Key Engineering Materials, Vol. 437, pp. 324-328, 2010