MICROWAVE ANALOG TO DIGITAL CONVERTER USING PARALLEL OPTICAL SAMPLING

WE PROPOSE TO DEMONSTRATE AN OPTICAL ANALOG-TO-DIGITAL CONVERTER FOR MICROWAVE ANALOG SIGNALS WHICH UTILIZES A SINGLE ELECTROOPTIC BROADBAND VELOCITY MATCHED TRAVELLING WAVE MODULATOR BUT WITH MULTIPLE PULSED OPTICAL BEAMS TO SAMPLE THE SIGNAL AND MULTIPLE STANDARD ELECTRONIC A/D'S TO ACCOMPLISH THE CONVERSION IN PARALLEL. THE DIGITAL OUTPUT WORDS APPEAR ON MULTIPLE SETS OF LINES APPROPRIATE FOR A MASSIVELY PARALLEL DIGITAL SIGNAL PROCESSOR. THIS DESIGN AVOIDS CERTAIN WEAKNESSES EVIDENT IN PAST OPTICAL AND ELECTRONIC A/D'S SUCH AS NO VELOCITY MATCHING OF THE OPTICAL AND MICROWAVE FIELDS, SERIAL PROBLEMS SUCH AS DIGITAL DATA LINES RUNNING AT MICROWAVE SPEEDS, ANY ELECTRONICS WORKING AT THE MICROWAVE SAMPLING SPEEDS, OR AMBIGUITY CAUSED BY USING AN OPTICAL TECHNIQUE THAT DETERMINED THE BIT VALUES IN THE DIGITAL OUTPUT WORD INDEPENDENTLY OF EACH OTHER AND WAS THEREFORE SUBJECT TO GROSS ERRORS FROM SMALL AMOUNTS OF INTERNAL A/D NOISE OR EXTREMELY SMALL MISADJUSTMENTS. THE PROJECT OBJECTIVE IS THE DEMONSTRATION OF A TWO CHANNEL OPTICAL A/D THAT CAN BE EXTENDED IN SPEED BY A SIMPLE PARALLEL EXPANSION.