FIBEROPTIC CHLORIDE SENSOR DEVELOPMENT

Chloride in the form of salt water is a major contaminant of ground wa ter, percolating through landfill liners and causing corrosion of stee l. Four fiber-optic sensors capable of detecting chloride concentratio ns were developed. The most promising sensor detects chloride concentr ations from 100 mu g/mL to greater than 3,000 mu g/mL. This sensor wor ks when the chloride changes a reddish-brown silver chromate strip to white silver chloride. The color change causes the intensity of light propagating through the fiber to increase. The increase is monitored, and a calibration curve depicting light intensity versus chloride conc entration results. The most promising sensor was multiplexed to determ ine the diffusion coefficients of chloride in a saturated sand column. The development, operation, and sensitivity of the sensors are descri bed. Upon further development the sensor could be placed in the soil o r in reinforced concrete for in situ monitoring of chloride. The senso r's advantages over electronic sensors include immunity to corrosion a nd electromagnetic interference, and the ability for multiplexing sens ors onto a single fiber.