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Optical Displacement Sensor in a Capillary Covered Hollow Core Fiber Based on Anti-Resonant Reflecting Guidance

A capillary covered silica hollow core fiber (HCF) has been designed and tested for the measurement of displacement based on antiresonant reflecting optical waveguide. A section of the silica HCF was inserted into a silver coated capillary. A Fabry-Perot resonator can be formed in the silica cladding. The leaky mode of the guided light can be achieved at resonant wavelengths of the Fabry-Perot resonator, which results in lossy dips in the transmission spectrum. The transmission power of the dip is sensitive with the displacement of the capillary since the effective reflectivity of the Fabry-Perot resonator is affected by the location between the capillary and the silica HCF. The experimental results show that the sensitivity of up to 0.578 dB/μm is achieved, and the proposed sensor is insensitive with the temperature.