SYSTEMS AND METHODS FOR OPTICALLY GENERATED TRIGGER MULTIPLICATION

摘要

SYSTEMS AND METHODS FOR PROVIDING TRIGGER SIGNALS IN AN OPTICAL INTERROGATOR, WHEREIN MULTIPLE TRIGGERS ARE GENERATED WITHIN EACH PERIOD OF A VARYING REFERENCE SIGNAL, AND WHEREIN THE TRIGGERS ARE EVENLY SPACED ACCORDING TO THE WAVENUMBER OF THE REFERENCE SIGNAL. IN ONE EMBODIMENT, AN OPTICAL FREQUENCY DOMAIN REFLECTOMETRY SYSTEM PROVIDES A LASER BEAM TO A REFERENCE INTERFEROMETER TO PRODUCE A REFERENCE SIGNAL. THIS SIGNAL IS PASSED THROUGH A 4X4 OPTICAL COUPLER WHICH SPLITS THE SIGNAL INTO A FIRST SIGNAL AND A SECOND SIGNAL THAT IS 90 DEGREES OUT OF PHASE WITH THE FIRST SIGNAL. THESE SIGNALS ARE CONVERTED TO ELECTRICAL SIGNALS, AND A TRIGGER UNIT GENERATES TRIGGERS AT POINTS AT WHICH THE TWO ELECTRICAL SIGNALS HAVE ZERO-CROSSINGS, AND AT WHICH THE MAGNITUDES OF THE SIGNALS ARE EQUAL. THE RESULTING TRIGGERS REMAIN EVENLY SPACED WITHIN THE PERIOD OF THE REFERENCE SIGNALS, EVEN WHEN THE PERIOD IS CHANGED.