Reflective fiber refractometer based on fiber Bragg grating inscribed in thin-core-fiber
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A novel reflective refractometer based on a fiber Bragg grating (FBG) inscribed in a thin-core-fiber (TCF) stub was demonstrated. The cladding modes are excited by the core diameter mismatch between the single-mode-fiber (SMF) and TCF. The core mode and specific cladding modes in the TCF are reflected by the FBG and partly recoupled into the back-propagating core mode in the SMF. Experimental results demonstrate that the power of the cladding mode reflection changes with the surrounding refractive index (SRI). The temperature-immune SRI measurement with linear sensitivity of 54.55 dB per refractive index unit has been achieved by the cost-effective power detection within the refractive index range from 1.33 to 1.42. To eliminate the measurement deviation caused by the fluctuation of light source, the simple self-referencing detecting has been carried out by measuring the ratio of the cladding mode reflection and the core mode reflection.
KeywordsOptical fiber refractometer Fiber Bragg grating Thin-core-fiber Power-referenced
This work was supported by the Program of Zhejiang Leading Team of Science and Technology Innovation (No. 2010R50007), the National Natural Science Foundation of China (No. 61307053) and the China Postdoctoral Science Foundation (No. 2013M531866).
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