LAUSR

We demonstrate the fabrication of helical long-period gratings (HLPGs) with the periodic helical index modulation by twisting the double-clad fiber (DCF) while the fiber was exposed by CO2 laser. Torsion, bending, surrounding refractive index, temperature and axial strain characteristics of the fabricated DCF-HLPG were investigated experimentally. The DCF-HLPG was found to have a high torsion sensitivity of −0.384 nm/(rad/m) and bending sensitivity of 18.112 nm/m−1 due to the asymmetric helical index modulation across the fiber section induced by the CO2 laser heating.