In-Fiber Double-Layered Resonator for High-Sensitive Strain Sensing

A high-sensitive strain sensor based on the anti-resonant reflecting optical waveguide in a double-layered Fabry-Perot resonator is proposed and experimentally demonstrated. A section of the silica hollow core fiber with a small diameter was inserted into a polymethyl methacrylate hollow core fiber with a relative large diameter. A double-layered Fabry-Perot resonator can be formed between the silica cladding and polymethyl methacrylate cladding. Due to the photoelastic effect and thickness change of the cladding in the polymethyl methacrylate hollow core fiber, the resonant condition of the Fabry-Perot resonator is changed. The tensile strain is measured by interrogating the wavelength shift. The experimental results show that the resolution of the sensor can be achieved as 27.9 pm/με, and the temperature cross sensitivity is only 1.67 pm/°C. The proposed fiber sensor can be used for the accurate measurement of the strain.