WIDE DYNAMIC RANGE LASER DIODES FOR COMMUNICATIONS

WITH THE ADVENT OF LASERS IN COMMUNICATIONS, ONE TECHNIQUE THAT IS EMPLOYED IS DIRECT AMPLITUDE MODULATION OF THE SOURCE LASER WITH THE RF WAVE THAT ACTUALLY CARRIES THE INFORMATION OF INTEREST. DEMODULATION IS PERFORMED VIA DIRECT DETECTION OF THE RECEIVED BEAM FOR MANY SHORT-DISTANT COMMUNICATIONS. A LIMITATION ON THIS TECHNIQUE IS THE LINEARITY OF THE DIRECT MODULATION. THAT IS, THE AMPLITUDE OF THE OPTICAL CARRIER DOES NOT CORRESPOND TO THE AMPLITUDE OF THE INPUT RF IN A LINEAR FASHION. THIS NONLINEARITY CAN CAUSE DISTORTIONS, ESPECIALLY WHEN MANY CHANNELS ARE MULTIPLEXED IN THE RF PRIOR TO MODULATION. ONE METHOD TO CORRECT THIS PROBLEM IS A LASER DIODE DEVELOPMENT EFFORT TO CREATE DIODES WITH THE APPROPRIATE LINEARITY (1 PART IN 10,000). THIS, HOWEVER, CAN BE VERY COSTLY AND CAN DELAY THIS COMMUNICATION TECHNOLOGY FROM FUTURE DEVELOPMENT. A MORE COST-EFFECTIVE CORRECTION IS TO USE PRESENT TECHNOLOGY IN DIODE DEVELOPMENT AND CREATE THE NECESSARY LINEARITY THROUGH ELECTRONIC FEEDBACK. SCIENCE, INC. PROPOSES THIS APPROACH, BASED ON TECHNOLOGY RELATED TO THE STABILITY OF LASER POWER OUTPUT. THIS PROPOSAL DISCUSSES A NOVEL METHOD WHEREBY COMMERCIALLY-AVAILABLE ELECTRO-OPTIC COMPONENTS CAN BE PACKAGED TO PRODUCE THE EFFECTS OF A LASER DIODE WITH OUTPUT LINEARITY OF 1 PART IN 10,000 AND A BANDWIDTH OF 10 MHZ. ANTICIPATED BENEFITS/POTENTIAL COMMERCIAL APPLICATIONS - APPROPRIATE ELECTRO-OPTIC TECHNOLOGY ALONG WITH ELECTRONIC FEEDBACK OR FEEDFORWARD NETWORKS CAN PRODUCE THE APPROPRIATE MODULATION LINEARITY WITHOUT THE NEED FOR EXPENSIVE LASER DIODE DEVELOPMENT WORK. THEREFORE, THIS TECHNOLOGY WILL PROVIDE A COST-EFFECTIVE METHOD FOR CREATING FIBER OPTIC COMMUNICATION LINKS USING DIRECT DETECTION