LOW COST FIBER OPTIC DIGITAL POSITION SENSORS FOR APPLICATIONS TO FLY-BY-LIGHT CONTROL SYSTEMS

THE CURRENT TIME DIVISION MULTIPLEXER (TDM) APPROACH USED IN FIBER OPTIC DIGITAL POSITION SENSING USES EXPENSIVE AND TEMPERATURE SENSITIVE FIBER OPTIC DELAY LINES IN THE TRANSDUCER. PHYSICAL OPTICS CORPORATIOM (POC) PROPOSES A MODULAR WAVELENGTH DIVISION MULTIPLEXER (WDM) APPROACH WHICH USES A SINGLE PLANAR HIGH EFFICIENCY (>95%) VOLUME HOLOGRAM IN THE TRANSDUCER. THE HOLOGRAM, WHICH CAN OPERATE IN HIGH TEMPERATURE ENVIRONMENTS, DISPERSE THE BROAD (\200 NM) SPECTURM OF THE INPUT LIGHT FROM THE FIBER ONTO A CODE PLATE MOUNTED ON THE SENSOR MECHANISM. THE ABSOLUTE POSITION IS ENCODED BY THE REFLECTIVE/ABSORPTIVE TRACKS ON THE CODE PLATE WHICH CORRESPOND TO THE DIFFERENT WAVELENGTHS. A DEMULTIPLEXER AND A PHOTODETECTOR ARRAY DECODE THE MODIFIED REFLECTED OPTICAL SPECTRUM. POC IS A LEADER IN FABRICATING HIGH EFFICIENCY WDMS AND VOLUME HOLOGRAPHIC GRATINGS WHICH ARE REQUIRED FOR A PRACTICAL, LOW COST SYSTEM. THE WDM SYSTEM CAN BE ADAPTED TO SHORT (UNDER 1/3 INCH) OR LONG (OVER 6 INCHES) STROKE APPLICATIONS. IN PHASE I, POC WILL PROVIDE A DETAILED DESIGN AND TRADE-OFF ANALYSIS FOR THE ARMY'S APPROVAL. A PRELIMINARY PROTOTYPE WILL ALSO BE CONSTRUCTED AND EVALUATED FOR APPLICATIONS FLY-BY-LIGHT CONTROL SYSTEMS.