A DAMAGE SENSOR FOR HIGH POWER LASER DELIVERY FIBERS USING LOW-COST FLUORESCENT OPTICAL FIBERS

LARGE CORE SILICA FIBER OPTIC SYSTEMS ARE UNDER DEVELOPMENT FOR DELIVERING HIGH POWER LASER ENERGY FROM COPPER VAPOR LASERS TO DYE LASERS IN THE URANIUM-ATOMIC VAPOR LASER ISOTOPE SEPARATION (U-AVLIS) PROCESS. ALTHOUGH FIBER OPTIC SYSTEMS IMPROVE SAFETY AND MANUVERABILITY OF THE LASER BEAM, NO LOW-COST, NONINTRUSIVE METHOD EXISTS FOR MONITORING THE CONDITION OF THESE FIBERS. THIS PROJECT STUDIES THE USE OF FLUORESCENT PLASTIC OPTICAL FIBERS TO MONITOR LIGHT LEAKAGE OF THE LASER DELIVERY FIBERS. THE FLUORESCENT FIBERS RUN ADJACENT TO THE LASER POWER DELIVERY FIBERS, WITHIN THE POWER DELIVERY FIBER CABLE. PROPER SELECTION OF ORGANIC DYE ALLOWS THE PLASTIC OPTICAL FIBER TO FLUORESCE WHEN EXPOSED TO LASER LIGHT LEAKED OUT OF LASER DELIVERY FIBERS THAT HAVE BEEN DAMAGED OR BENT. BENDING FIBERS CAN BE USED AS AN OPTICAL POWER MEASUREMENT. THE FLUORESCENT SIGNAL WILL BE GUIDED BY THE PLASTIC OPTICAL FIBER TO A PHOTODETECTOR ARRAY AND DISPLAY PANEL. IN THE STEADY-STATE CONDITION, THE PHOTODETECTORS WILL RECEIVE VERY LITTLE LIGHT. DAMAGE TO ONE OF THE LASER DELIVERY FIBERS WILL CAUSE A FLUORESCENT SIGNAL TO BE SENT TO THE PHOTODETECTOR ARRAY, AND AN ALARM WILL BE ACTIVATED. A VERY SIMPLE SCHEME WILL ALLOW THE LOCATION OF THE PROBLEM IN THE POWER FIBER TO BE DETERMINED WITHIN A FEW FEET. THIS APPROACH TO FIBER OPTIC LASER DELIVERY MONITORING CAN ALSO SERVE AS AN OPTICAL POWER METER BY INCORPORATING A TEMPORARY CALIBRATED BEND INTO THE LASER DELIVERY FIBER. IN THIS MANNER, IT WILL COUPLE A FRACTION OF THE COPPER VAPOR LASER ENERGY OUT OF THE LASER DELIVERY FIBER AND EXCITE A PROPORTIONAL AMOUNT OF OPTICAL FLUORESCENCE IN THE PLASTIC OPTICAL FIBER. THIS MONITORING SYSTEM WILL BE PASSIVE, SELF-VERIFYING, RUGGED, AND VERY COST-EFFECTIVE. IN PHASE I, A WORKING MODEL OF THE DAMAGE SENSOR IS BEING CONSTRUCTED BY ATTACHING PIGTAILED FLUORESCENT FIBERS TO A SECTION OF POWER FIBER CARRYING SIMULATED COPPER LASER LIGHT. THE MODEL WILL BE TESTED BY INDUCING VARIOUS TYPES OF BENDS AND DAMAGE IN THE POWER FIBER.