Compact fiber strain sensor fabricated by a CO<sub>2</sub> laser
Senyu Wang, Yiwei Ma, Tao Geng, Cuiting Sun, Hongjia Zhu, Xiaoyang Li, Yi Yang, Shuo Zhang, Weimin Sun, Libo Yuan
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">C</mml:mi> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext>ε</mml:mtext> </mml:math> in the dynamic range of 0–425 µ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mtext>ε</mml:mtext> </mml:math> . Meanwhile, the temperature sensitivity of PIP-LPFG is 54.7 pm/°C in the dynamic range of 30–170°C.