Preparation of Adiabatic Microfiber Bragg Grating by Chemical Etching

Micro fiber Bragg grating (MFBG) is sensitive to temperature and refractive index at the same time, and has excellent sensing performance. Scholars all over the world have carried out a lot of research on it. At present, for the preparation of adiabatic MFBGs, micro fibers meeting adiabatic conditions are prepared by heating stretching method, and then fabricated by mask method or etching method. In order to simplify the preparation process, based on chemical etching method, a simple and easy technique for preparing adiabatic MFBG is proposed. In this technique, the FBG immersed in corrosion solution is gradually lifted by stepping motor, which can form a transition region with decreasing diameter, so that the cone angle of the transition region meets the adiabatic conditions, and then an adiabatic MFBG is formed. Several adiabatic MFBGs with different diameters are actually fabricated. The results show that adiabatic MFBG has better spectral and wavelength stability than ordinary MFBG. Finally, the refractive index and temperature sensing of the MFBGs are realized, the results showed that for MFBG with a diameter of about 9 μm, its sensing sensitivity to refractive index and temperature are 5200 pm/RIU and 10.06 pm/°C, for MFBG with a diameter of about 12 μm, the sensing sensitivity are 1125 pm/RIU and 10.33 pm/°C.