Chirped Fiber Bragg Grating (cfbg) by Etching Technique for Simultaneous Temperature and Refractive Index Sensing

This paper presents the fabrication of chirped Fiber Bragg Grating (CFBG) from uniform Fiber Bragg Grating (FBG) by etching technique in order to utilize it as refractive index sensors. Etching is carried out with the presence of a layer of silicone oil on top of the hydrofluoric acid to achieve partial-etching of the FBGs. The partiallyetched FBGs exhibit two different modes: fundamental mode from the FBG region still protected by fiber cladding; modes excited by exposed FBG region due to different effective index. The CFBG has a temperature sensitivity of 0.021nm/°C. Refractive index response is also tested by immersing the CFBG into liquid with refractive index ranging from 1.328 to 1.370 and it is found that only modes excited by exposed FBG region respond linearly to refractive index change. This characteristic shows that the CFBG can be used for simultaneous sensing of temperature and refractive index.