IGF::OT::IGF CONVENTIONAL PPM LASER TRANSMITTERS, A CW LASER FOLLOWED BY A MODULATOR, ARE INHERENTLY INEFFI…

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IGF::OT::IGF CONVENTIONAL PPM LASER TRANSMITTERS, A CW LASER FOLLOWED BY A MODULATOR, ARE INHERENTLY INEFFICIENT SINCE THE DATA MUST BE CARVED FROM THE LASER'S STEADY OUTPUT. 95% OF THE OPTICAL POWER IS DISCARDED IN A STANDARD TELECOM RZ FORMAT, WITH ANOTHER 8X EFFICIENCY REDUCTION USING A PPM SCHEME. AN ALTERNATIVE IS TO FORM THE PULSE TRAIN WITH A MODE-LOCKED LASER. HOWEVER, SINCE THE RESULTANT MLL PULSE TRAIN IS PERIODIC, IT MUST PRODUCE PULSES IN EVERY SYMBOL SLOT, NOT JUST ONCE PER SYMBOL. THIS MEANS THAT FOR A 32-ARY PPM SCHEME, THE MLL OPTICAL EFFICIENCY IS REDUCED BY A FACTOR OF AT LEAST 32 BY DISCARDING THE UN-NEEDED PULSES. IN BOTH CASES, THE ELECTRO-OPTIC MODULATOR ITSELF INDUCES AN ADDITIONAL 60% OPTICAL LOSS, AND REQUIRES NEARLY 0.5W OF POWER TO DRIVE. AN ALTERNATIVE IS TO USE A LOW-REPETITION-RATE MLL IN COMBINATION WITH A SWITCH FABRIC TO DELAY EACH OUTPUT PULSE INTO THE CORRECT PPM SLOT. HOWEVER, THE USE OF PHOTONIC INTEGRATED CIRCUITS (E.G., SILICON) IS PROHIBITIVE DUE TO THE HIGH INTRINSIC LOSS. A 100-MHZ PPM DATA RATE SCHEME REQUIRES ~5NS PULSE DELAY. THIS REPRESENTS 43-CM PROPAGATION IN SILICON, INDUCING A POWER LOSS OVER 10 DB. ADDING THE LOSS DUE TO SPIRALED DELAY LINES, SWITCH JUNCTIONS, AND COUPLING ON/OFF CHIP, THE AGGREGATE LOSS OF THE SWITCH FABRIC IS 18 TO 24 DB, REPRESENTING A SIGNIFICANT EFFICIENCY LOSS. RAM PHOTONICS PROPOSES THE DEVELOPMENT OF A QUALITATIVELY NOVEL APPROACH TO HIGH-EFFICIENCY, LOW-BIT-RATE LASER TRANSMITTERS COMPATIBLE WITH SPACE-BORNE MISSIONS. SPECIFICALLY, WE PROPOSE TO DEVELOP A LASER TRANSMITTER THAT ATTAINS HIGHLY EFFICIENCY OPTICAL DATA GENERATION BY (1) GENERATING ONLY ONE OPTICAL PULSE PER SYMBOL AT ARBITRARY TEMPORAL LOCATION, (2) ELIMINATING ALL ELECTRO-OPTIC MODULATORS, AND (3) EXPLOITING NEW ADVANCES IN FIVER OPTIC AND OPTO-ELECTRONIC PACKAGING. THE NEW TRANSMITTER DEVICE HAS LOW DISSIPATION (<0.5 W TOTAL) AND LOW SWAP FOOTPRINT, AND CAN OPERATE AT ARBITRARY DATA RATES AND GENERATE ANY SYMBOL FORMATS