Highly Sensitive Temperature-Independent Strain Sensor Based on a Long-Period Fiber Grating With a CO $_{2}$ -Laser Engraved Rotary Structure

We present a highly sensitive strain sensor based on the use of a long-period fiber grating (LPFG) with rotary grooves carved by high-frequency CO₂-laser pulses. We observe that, when the rotation rate of the grooves is sufficiently large, the resonance peak of the grating splits into two with a wavelength separation that changes sensitively with the strain applied along the grating and remains practically constant with a change in the ambient temperature. By measuring the wavelength separation of the two resonance peaks, we obtain a strain sensitivity of ~0.1067 plusmn 0.0075 nm/mu epsiv without any temperature compensation, which is larger than that of a conventional LPFG by almost two orders of magnitude.