Optical Fiber Coupler With a Hollow Core Fiber for Magnetic Fluid Detection

A new type of optical fiber coupler composed of a conventional solid core fiber and a hollow core fiber (HCF) is proposed. The hollow core of the HCF can be filled with various functional liquids and thus provides flexibility in tuning the guiding properties of photons. This enables the proposed coupler to be used as a versatile fiber sensing device. The experimental results revealed its sensitivity to be 73 000 nm/RIU. Compared with a vibrating sample magnetometer with a sensitivity of 10-7emu and accuracy of ± 1% in the magnetic sensing, the new fiber coupler was estimated to have a higher sensitivity of 2.4 × 10-10emu and an accuracy of ± 1.3 × 10-2% under an optimal performance condition in a conventional optical spectrum analyzer.