PH Sensor using Fiber Bragg Grating based on Swelling of Hydrogel

To achieve pH detection of multi-points, a new pH sensor based on pH sensitive hydrogel swelling detection by a fiber Bragg grating is proposed. The deflection of a silica membrane due to pH value change induced hydrogel swelling is measured by the center wavelength shifts of a fiber Bragg grating epoxied on the membrane. The relation between center wavelength shifts of the fiber Bragg grating with the hydrogel swelling behavior was studied experimentally. Around 100pm shift of the fiber Bragg grating center wavelength was observed when the pH value was changed from 4 to 7 or from 7 to 10 by using pH standard solutions, which fundamentally proved the feasibility of this method for pH detection.