LASER RF OPTICAL LINKS FOR AOTH RADAR

THE USE OF HIGH-GAIN ANTENNA ARRAYS FOR ADVANCED OVER-THE-HORIZON (AOTH) RADAR IS COSTLY BECAUSE OF THE LARGE PHYSICAL EXTENT OF THE ARRAYS AND BECAUSE OF THE CONSTRUCTION COSTS FOR A LARGE NUMBER OF ELEMENTS, EACH REQUIRING A RECEIVER AND POWER SOURCE. MICRILOR WAS AMONG THE FIRST TO SUGGEST THE USE OF MACH/ZEHNDER INTERFEROMETERS (MZI) FOR PASSIVE TRANSDUCTION OF ANTENNA ELECTRICAL SIGNALS TO CONVEY THESE SIGNALS TO A MORE-CONVENIENT RECEIVING SITE; THIS TECHNIQUE APPEARS PROMISING FOR A VARIETY OF ANTENNA-REMOTING APPLICATIONS. FOR REMOTING RECEIVE ELEMENTS FOR A LARGE OTH APERTURE, HOWEVER, THE USE OF DIRECT-LASER MODULATION APPEARS TO OFFER ADVANTAGES OVER THE MZI APPROACH. THE PROJECTED COST OF REMOTING RECEIVE ELEMENTS USING HIGH-DYNAMIC-RANGE LASER DIODES IS ABOUT $2K PER ELEMENT, COMPARED TO ABOUT $30K PER ELEMENT USING THE MZI APPROACH. WHILE MZI LINKS ARE THUS UNLIKELY TO PROVIDE COST SAVINGS COMPARED TO STANDARD RF CABLING, THE USE OF DIRECT-LASER MODULATION FOR CONVEYING RF SIGNALS IN AOTH COULD SAVE AN ORDER OF MAGNITUDE IN COST. THE PROPOSED PROGRAM WOULD STUDY APPLICABLE APPROACHES AND EVALUATE THE MOST-PROMISING COMMERCIAL LASER DIODE. THIS WORK COULD RESULT IN MORE-GENERAL APPLICABILITY OF COMMERCIAL PHOTONICS TECHNOLOGY TO MILITARY PROGRAMS, LOWERING COSTS AND ENSURING INDUSTRIAL SOURCES. FUTURE GOVERNMENT-SPONSORED RESEARCH IN THIS AREA WOULD ALSO CONTRIBUTE TO U.S. COMPETITIVE POSTURE.