Analysis on strain sensing characteristic of long period fibre grating based on deep-grooved process

Abstract

In this paper, the strain sensing characteristic of long period fibre grating (LPFG) based on deep-grooved process was investigated. The core sensitivity of LPFG was fabricated by a high frequency focused and improved CO2 laser irradiation system in ways of periodic and spaced heating on the ordinary single-mode fibre. Combined with the mobile platform and optical measurement platform with high precision, this paper built an optical fibre strain sensor measurement system based on the deep-grooved modulation and it was focused on the deep-grooved LPFG. According to use finite element analysis software to model and static simulation for the grooved fibre grating, the strain distributed contours and the degree of the micro-bend at the grooved structure section can be obtained. The principal research and experimental testing demonstrated that the grooved fibre grating would produce micro-bend structure with the axial strain increasing, which formed some types of corrugated structure, and resonant wavelength could blue shift by according to the elasto-optical effect. Such a measurement system of deep-grooved LPFG strain sensor had a high sensitivity and the average strain sensitivity of resonant wavelength was up to –10.28 pm/με, which was increased by 22.85 times than strain sensor based on the without depth of grooves. It offers practical value in engineering applications.