Bending and Strain Sensitivities in a Helicoidal Long-Period Fiber Gratings

Abstract

In this letter, we report bending and strain sensitivities of helicoidal long- period fiber gratings fabricated by twisting single- mode fibers during CO(2) laser irradiation. Linear spectral shifts of the resonant wavelengths under the bending and tensile strain were observed with the sensitivities of 11.7 nm/m(-1) and 1.1 pm/mu epsilon, respectively. The corresponding transmission power variations at the resonance wavelength were 4.1 dB/m(-1) and 2.2 x 10(-4) dB/mu epsilon, respectively. Detailed measurement techniques and sensor applications are discussed.