All-fiber pH Sensor Based on Hydrogel Swelling Characteristics in Optical Sagnac Loop
An optical fiber Sagnac loop pH sensor based on the swelling stress of hydrogel is developed,select-ing polyacrylamide hydrogel with favorable swelling performance as the sensing medium,considering the differen-tial swelling of hydrogel in solutions with varying pH values.The differential swelling of the hydrogel in various pH solutions induces a change in the axial stress of the polarization-maintaining fiber to lead to spectral shifts in the Sa-gnac loop output.By characterizing the spectral shift,pH sensing is achieved.The sensor exhibits a linear response within the pH range of 2 to 12,with a sensitivity of 0.947 nm/pH.Experimental results show that it has good robust-ness,stability and repeatability.
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