Optical hydrophone with digital signal demodulation
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsDavid J. Moretti, Michael Amaral, Antonio L. Deus, III, Gerald L. Assard
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Abstract
A system for digitally demodulating optical hydrophone signals is provided. The system includes an optical hydrophone connected to an analog-to-digl converter and further connected to a digital signal processor. Within the digital signal processor, a basic demodulator has a first and second mixing tables, the first table operating at a modulating frequency, .omega., injected into reference legs of the hydrophone, and a second table operating at 2.omega.. The mixer frequencies are coherently mixed with the incoming acoustic signals received by the hydrophone. An automatic calibration circuit which adjusts the phase of the mixers is connected to the basic demodulator.
Claims11
An optical hydrophone system comprising:
- an optical interferometer;
- an analog-to-digital converter connected to said optical interferometer;
- and
- a digital signal processor connected to and receiving output signals from said analog-to-digital converter, said digital processor including a basic demodulator module located within said digital signal processor and a calibration module located within said digital signal processor and connected to said basic demodulator.
An optical hydrophone system as in claim S wherein said basic demodulator further comprises a first low-pass filter receiving the output of said first mixer table and a second low-pass filter receiving the output of said second mixer table.
Dependencies are inferred from the claim text.