Exoskeleton type long-period fiber grating for cross-talk-resistance single-parameter measurement

Abstract

This paper proposes a new, to the best of our knowledge, design framework of long-period fiber grating (LPFG) sensors resistant to multi-parameter cross talk. A section of hollow quartz capillary (HQC), which acts as an exoskeleton, is periodically merged with a single-mode fiber (SMF) by the arc-discharge method. The mechanical stress in the SMF is released while the thermal stress is enhanced after a high-temperature fusion process. Under the influence of the elastic-optical effect, the refractive index of the core is periodically modulated along the axial direction to form an exoskeleton long-period fiber grating (Es-LPFG). The unique exoskeleton structure not only induces mode coupling but also enables the proposed device to resist cross talk among the strain, ambient refractive index, and vector bending. The temperature is able to be measured independently with a sensitivity of 74 pm/∘C. The novel Es-LPFG is promising in single-parameter sensing, mode-locked lasers, and frequency-locked gain flattening.

An Axial Force Sensor Based on a Long-Period Fiber Grating with Dual-Peak Resonance

“…Long-period fiber gratings (LPFGs) allow for the co-propagating coupling of the core mode with several cladding modes [12]. It enables the LPFGs to have sensitivity to many environmental parameters, such as temperature, strain, bending, torsion, surrounding refractive index (RI), and force [13]. For axial force measuring, a silica SMF-based LPFG with a force sensitivity of ~0.5 nm/N has higher sensitivity than that of a traditional FBG.…”