Experimental Study on Etching of Fiber Bragg Grating for Sensing Application

Abstract

Optical fiber sensors are popular due to its attractive feature. Chemically wet Etched Fiber Bragg Grating (EFBG) finds wide application in chemical and biochemical sensing domain. This paper demonstrate for the first time use of low cost high plastic polymer to hold FBG during wet chemical etching process. Experiment reveals etching rate of 4.7 µm/min for SM1500 (4/125) fiber using hydrofluoric (HF) 48% at room temperature. Original Bragg wavelength \( (\lambda_{B} ) \) of 1547.528 nm shifts to 1548.322 nm and 1547.097 nm after etching for 15 min and 25 min. Shift in Bragg wavelength during etching process found not be linear. Initial red shift is noticed due to heating interaction and final blue shift is due to evanescent field interaction with HF. The use of EFBG for sensing surrounding refractive index (R.I.) for deionized water is experimentally demonstrated. It provides red shift of 0.067 nm. This low cost, fast, accurate, homogeneous, in house, indigenously adopted wet chemical etching process can be applied on photosensitive optical fibers for developing RI based biosensor and chemical application.