Fiber-optic refractive-index sensors based on transmissive and reflective thin-core fiber modal interferometers |
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Authors: | Tian-Hao Xia Bobo Gu |
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Institution: | a Centre for Optical and Electromagnetic Research, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, PR China b School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, PR China |
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Abstract: | We present a new fiber-optic refractive-index sensor based on a fiber modal interferometer constituted by a thin-core optical fiber, whose cut-off wavelength is around three times shorter than normal single-mode fiber. In such a core diameter mismatching structure, the high-order cladding modes are efficiently excited and interfere with the core mode to form a high extinction-ratio filter (>30 dB). Both transmissive and reflective thin-core fiber modal interferometers are experimentally demonstrated, and show a high sensitivity to a small change of external refractive-index (>100 nm/R.I.U.), but a low sensitivity to the change of temperature (<0.015 nm/°C). Such a fiber device possesses an extremely simple structure, but excellent refractive-index sensing properties, and thus is an ideal candidate for fiber-optic biochemical sensing applications. |
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Keywords: | Fiber-optic interferometer Optical fiber sensor Refractive-index sensor |
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