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Characterization of fiber Bragg grating sensor for pH measurement

A wavelength modulated optical pH sensor is presented. The sensor comprises fiber Bragg grating (FBG) coated with pH sensitive hydrogel. The sensing principle relies on wavelength shifts resulted from the induced strain on the FBG due to mechanical expansion of the hydrogel. The pH response of the sensor was simulated using free energy function by employing finite element method. Experimental work was carried out to investigate the pH response, time response, and temperatures cross sensitivity of the sensor. The results show that the sensor has a good reversibility and provides linear response in pH range of 5 to 7 with sensitivity of 0.114nm/pH unit.