Compact fiber strain sensor fabricated by a CO2 laser

Abstract

In this Letter, a novel, to the best of our knowledge, parallel inclined planes long period fiber grating (PIP-LPFG) for strain measurement is proposed. This structure is fabricated by a high frequency ${{\rm CO}_2}$ laser, which has polished periodic parallel inclined planes on a single mode fiber (SMF). Refractive index modulation (RIM) over a large area on the surface of the SMF significantly shortens the total length of the grating, and the structure of parallel inclined planes efficiently enhance the strain sensitivity of PIP-LPFG. Experimental results show that this LPFG with a miniature length of 3.9 mm has a good repeatability and stability of strain response, which can reach to 116 pm/µ$\unicode{x03B5}$ in the dynamic range of 0–425 µ$\unicode{x03B5}$. Meanwhile, the temperature sensitivity of PIP-LPFG is 54.7 pm/°C in the dynamic range of 30–170°C.