FIBEROPTIC SONAR DOME PRESSURE TRANSDUCER

THE HIGHEST PERFORMANCE PRESSURE SENSORS PRESENTLY IN USE UTILIZE A VIBRATING QUARTZ CRYSTAL TUNING FORK AS THE SENSOR. THE TUNING FORK IS DRIVEN ELECTRICALLY AT ITS RESONANT FREQUENCY WHICH SHIFTS IN PROPORTION TO PRESSURE APPLIED TO IT. QUARTZ TUNING FORKS ARE ALSO USED AS TIMING ELEMENTS IN ELECTRONIC WATCHES. STANDARD MICROELECTRONIC FABRICATION TECHNIQUES ARE WELL DEVELOPED AND HIGHLY REPRODUCIBLE QUARTZ OSCILLATORS CAN BE FABRICATED AT REASONABLE COST. PRESSURE SENSORS OF THIS TYPE EXHIBIT EXTREME STABILITY, WIDE DYNAMIC RANGE, EXCELLENT LINEARITY AND VERY HIGH PRECISION. SUCH SENSORS ARE PRESENTLY MANUFACTURED FOR RUGGED USES SUCH AS IN DEEP SEA, AEROSPACE AND DOWNHOLE MEASUREMENTS. THE PROPOSED FIBEROPTIC SENSOR IS THE OPTICAL ANALOG OF THIS PRESSURE SENSOR. IT'S OSCILLATOR CIRCUITRY IS POWERED BY LIGHT FROM AN LED. A SECOND LIGHT BEAM, SHUTTERED BY THE VIBRATING TINES OF THE TUNING FORK, DETECTS THE SHIFT IN FREQUENCY OF OSCILLATION. SINCE THE MEASUREMENT IS INHERENTLY "DIGITAL", IT IS INSENSITIVE TO INTENSITY CHANGES. THE PROGRAM WILL FOCUS ON OPTICAL AND MECHANICAL DESIGN OF THE SENSOR AND DESIGN OF THE OPTOELECTRONICS PACKAGE TO POWER AND MEASURE THE FREQUENCY SHIFT OF THE SENSOR.