Analysis and Comparative Study of Intermittent-Spiral Long Period Fiber Grating

A torsion sensor based on intermittent-spiral long period fiber grating (IS-LPFG) is proposed based on the interaction mechanism of elliptical birefringence (IMEB). The IS-LPFG is fabricated by periodically polishing the four mutually orthogonal surfaces of a pre-twisted single-mode fiber (SMF) by CO
₂
laser. The interaction of birefringence caused by the intermittent-spiral distribution and the individual spiral structure determines the performance of torsion sensing. The torsion sensitivity reaches to 0.15 nm/(rad/m) in the case of superposition-IMEB, but also decreases to 0.08 nm/(rad/m) in the case of counteraction-IMEB. The experimental results are highly consistent with the simulation results. Through the exploration of the interaction of elliptic birefringence, it provides us with a method to control the birefringence in the fiber and improve the fiber torsion sensitivity based on H-LPFG.