Highly sensitive temperature-independent strain sensor based on a long-period fiber grating with a CO2-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±0.0075 nm/με without any temperature compensation, which is larger than that of a conventional LPFG by almost two orders of magnitude. © 2009 IEEE.