A Long-Period Fiber Grating Sensor Based on a Core-Cladding Misalignment Structure

In this article, a novel long-period fiber grating (LPFG) sensor based on a core-cladding misalignment structure is described. The LPFG consists of multiple short-length singlemode fiber (SMF) segments joined with core-cladding misalignment splicing. Due to the refractive index (RI) difference between the core and the cladding, periodic RI modulation along fiber axis is achieved. The resonance wavelength responses of the core-cladding misalignment structure based LPFG to RI, strain and temperature are investigated experimentally, and a maximum RI sensitivity of 992.8 nm/RIU, a strain sensitivity of -7.4 pm/μϵ, and a temperature sensitivity of -31 pm/°C are obtained, respectively. Such a core-cladding misalignment structure provides a low-cost fabrication route for LPFGs while offering high sensitivities, which has potential applications for accurate measurement and sensing in industrial and harsh environments.