Design and characterization of pH sensor based on sol-gel silica layer on plastic optical fiber

In this paper, design and characterization of a pH optical fiber sensor with pH sensitive dye is described. The sensor is prepared by fixing the doped plastic fiber on a fused ortosilica block surface with blue bromophenol. The surface charge of silica and the refractive index, which plays an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. We use the transmittance to measure the pH of a solution or fluid in a range between 5.0 and 7.0. The advantage of this sensor is that, only 2 cm of doped fiber is enough to measure the pH of a fluid in real time. The time response of the sensor reported in the present study is approximately 10 s.