AN OPTICAL BATHYTHERMOGRAPH

IT IS PROPOSED TO DEVELOP OPTICAL TEMPERATURE AND PRESSURE SENSORS FOR AN OCEANOGRAPHIC INSTRUMENT (AN OBT) THAT WILL MEASURE TEMPERATURE AND DEPTH DURING THE TIME OF FALL OF THEINSTRUMENT. THE TRANSMISSION LINK WILL ALSO BE OPTICAL FIBER. THE PRINCIPLE OF THE SENSORS INVOLVES THE MODULATIONOF THE BAND EDGE OF TWO TYPES OF OPTICAL FILTERS BY TEMPERATURE AND PRESSURE CHANGES OF THEIR ENVIRONMENT. THE PROJECTED INITIAL ACCURACIES ARE: 0.15 DEGREES FOR TEMPERATURE AND 3 DB FOR PRESSURE. THE PROJECTED PRODUCTIONCOST FOR A 450 METER PROBE IS IN THE $150 RANGE WITH THE COST DIMINISHING AS THE COST OF OPTICAL FIBER APPROACHES THAT OF COPPER WIRE AND AS THE PRODUCTION VOLUME INCREASES. THE NEED FOR SUCH AN INSTRUMENT ARISES FROM THE VULNERABILITY OF THE PRESENT ELECTRICAL EXPENDABLE INSTRUMENTS TO INSULATION LEAKS, AS WELL AS FROM THEIR INABILITY TO MEASURE PRESSURE. FURTHERMORE, THE FUTURE POTENTIAL OF FIBER OPTICS AND OPTICAL SENSORS IN REGARDS TO VERSATILITY, DATA RATE, AND COST IS COMPELLING. THE DEVELOPMENT OF A REFRACTION SENSOR FOR THE OBT TO PROVIDE A DENSITY MEASUREMENT IS ALREADY UNDERWAY, AND THE INCLUSION OF ALL THREE SENSORS IN AN UNDERWATER OPTICAL FIBER SENSING AND TELEMETRY NETWORK IS BEING EXPLORED.