High Sensitivity Chiral Long-Period Grating Sensors Written in the Twisted Fiber

A chiral long-period grating (CLPG) was fabricated successfully by scanning CO
₂
laser in a twisted conventional single-mode fiber. The strong mode coupling can be achieved in a short grating length. The sensing characteristics of the CLPGs were investigated experimentally. Compared with the conventional long-period fiber gratings, the CLPGs were found to have the similar temperature and refractive index sensitivities and much higher torsion, bending, and strain sensitivities. The high sensitivity of the CLPG can be attributed to the screw-type waveguide structure induced by the scanning laser in the twisted fiber. The proposed CLPGs could have great potential applications as filters and optical sensors.