Improvement of sensitivity and stability of fiber optic oxygen sensing based on cladding fluorescence

An attempt has been made to improve the sensitivity and stability of optical fiber sensor used for the continuous monitoring of gaseous oxygen. It utilizes the quenching phenomena of cladding fluorescence. Two polymers viz. poly cyclohexyl methylacrylate (PCMA) and poly (4-methyl-1-pentene) (PMP) were selected which were doped with 9,10-diphenyl anthracene (DPA) and sensor head was prepared by dipcoating the polymer on a 4.2 cms length of an especially designed ARTONTM plastic fiber with 1 mm core diameter. For dipcoating, polymer matrix containing 3% wt of fluorescent dye was used. The sensor head thus prepared was tested for various oxygen concentrations varied by mixing nitrogen. D2lamp was used for UV side pumping and thus the fluorescence generated in the cladding was coupled to another plastic optical fiber at the output end. The change in fluorescence due to oxygen content was recorded using a photo-multiplier at the (lambda) equals 430 nm. The results obtained have been tabulated in the form of comparative studies. The response was found to be fast, reversible and reproducible with recovery time of the order of few seconds in both the cases. The sensors were found to detect a wide range of oxygen concentration ranging from 0.5% to 100% of O2. In the case of PCMA, better stability in long-term was observed. The effect of cladding thickness on the sensor performance was also explored.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.