A biofilm sensor based on the single-end etched fiber Bragg grating(FBG) is proposed and is used for simultaneous measurement of biofilm thickness and temperature in the biofilm reactor.The theoretical model for the simultaneous measurement of surrounding refractive index(SRI) and temperature by the single-end etched FBG is presented,and the linear approximation for the SRI sensitivity is given.A single-end etched FBG with the diameter of the etched region of approximately 7.1-7.4 μm was fabrica...