Theoretical Study on the Fabrication of Core-Etched Fiber Bragg Grating Refractive Index Sensors

The characteristics of Bragg wavelength movement in the core-etched process of fiber Bragg grating (FBG) are theoretically calculated and analyzed under several different conditions. The numerical analysis shows that, the Bragg wavelength decreases non-linearly and more and more faster as the decrease in core diameter, furthermore, the decreasing speed and decreasing degree in Bragg wavelength are higher for the core-etched FBG with a lower surrounding refractive index (SRI) than that with a higher SRI. In addition, the variation of Bragg wavelengths are almost identical in the core-etched FBG of different grating period when other conditions being the same. These theoretical results would provide valuable guidance to the research on the fabrication and applications of core-etched FBG refractive index sensors by hydrogen fluoride (HF) solution etching.