| Summary: | 碩士 === 國立聯合大學 === 光電工程學系碩士班 === 100 === We have proposed a multimode fiber interferometer (MMFI) based on a single-mode fiber (SMF) splicing a section of no-core fiber (NCF) /multimode fiber (MMF) for sensing application. The interference mechanism of the proposed MMFI is according to the re-imaging theory. The developed device is capable of measuring the refractive index (RI) of the surrounding with (1)lower than、(2) higher than and even (3) index-matched that of the NCF. In particularly, by utilizing appropriate IR of the surrounding around the MMFI, it is possible to support the above three properties in the device when a broadband light source launches. The MMFI performs an ultrasensitive sensing in variations of the surroundings. Index-matching at a single wavelength yields a strong coupling of wavelength dip with a narrow bandwidth and a high extinction ratio (ER) of over 25dB. The wavelength dip also can be effectively tuned, greatly shifting with a variation in temperature (T) or refractive index (RI), when the index-matched condition is satisfied. This work demonstrates that the proposed sensor responds sensitively to T with an extremely high tuning efficiency of 50nm/°C and an excellent sensitivity to RI of 113.5μm per refractive index unit (RIU).
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