Refractive Index Sensor Based on Fiber Bragg Grating in Hollow Suspended-Core Fiber

A fiber Bragg grating (FBG) has been fabricated in a hollow suspended-core fiber (HSCF). The HSCF is suitable for refractive index sensor because its core is exposed in the large air hole, which can be used as a microfluidic channel. The refractive index sensitivity of the grating is 8.9 nm/RIU in the range from 1.41 to 1.44. The strain and temperature sensitivities of the HSCF-FBG are 0.8648 pm/με and 9.089 pm/°C, respectively, which are similar to the traditional single-mode fiber FBGs. Remarkably, the bending characteristic of HSCF-FBG has a great dependence on the bending direction and the maximum bending sensitivity is 84.11 pm/m-1. Therefore, the proposed HSCF-FBG can be also utilized as a bending sensor with direction recognition.