Optical fiber cone taper tip sensor for refractive index measurement

Optical fiber cone taper (OFCT) tip for refractive index sensing based on Michelson interferometer (MI) has been reported in present work. The fiber tip has been fabricated using chemical etching techniques, where hydrofluoric acid (HF) has been used as chemical etchant and silicone oil as protective layer for single mode fiber. The variation between intensity and refractive indices have been studied for small volume of liquid at operating wavelength 1550 nm and 1310 nm. In addition OFCT tips have been tested for pH detection and time response. The refractive index sensitivity of 9878.28 dB RIU-1 has been observed for sodium chloride (NaCl) solution in water of refractive index range from 1.3330 to 1.3342. Such kind of sensors using optical fiber tips are of low cost, simple fabrication and compact structure with high sensitivity. (author)