Long-term renewable sol-gel fluorescent optical fiber pH sensor

The construction and the operation properties of an organically doped, sol-gel cladded optical fiber pH sensor, are described. The silica-entrapped indicator in the fluorescence-based device was fluorescein, pumped with a continuous wave (cw) argon 488 nm laser. The transmitted signal through the sensing fiber yielded a response in the pH range of 4 - 7, where signal level increased from acid to base. The device is durable and renewable. When tested over more than 8 weeks it retained its response, as demonstrated by dozens of cycles of measurements each lasting a few hours. The probe is easily prepared under regular room conditions by simple decladding of the fiber and sol-gel recoating. System design and setup are attractive due to modularity and discardable low cost probe tips.