Strongly coupled multicore fiber with FBGs for multipoint and multiparameter sensing

A compact optical fiber sensor by embedding fiber Bragg gratings (FBGs) in strongly coupled multicore fiber (SCMCF) is proposed for multipoint and multiparameter sensing. To build the device, two FBGs with different peak wavelengths were inscribed in a segment of SCMCF. Then one end of the SCMCF was fusion spliced to a single-mode fiber (SMF) and the other end of the SCMCF was cleaved. In the SMF-SCMCF structure, two supermodes are excited, as a result, the reflection spectrum exhibits a sinusoidal pattern with two sharp peaks. The wavelength position of the FBGs and the supermode coupler can be extracted simultaneously. Two distinct FBGs inscribed in different positions of the SCMCF were used to demonstrate quasi-distributed multipoint sensing in the proposed structure. To the best of our knowledge, this is the first demonstration of an optical fiber sensor that combines FBGs with SCMCF. The sensor here proposed has the advantage of compact size, low-cost, good mechanical strength and ease of interrogation.