A free space optical communications system: An M-ary multi-pulse width Modulation scheme with emphasis on optimizing transmit power

Abstract

This effort investigates the development of a point-to-point, asynchronous pulse-mode communication system via a unidirectional, terrestrial free space optics link, utilizing a tunable, mid-IR Quantum Cascade Laser (QCL), courtesy of Daylight Solutions, Inc. In the current demonstration and simulations, this pulse communication scheme harnesses the availability of 24 unique pulse widths to achieve a variable bit rate, limited from 9.4 to 50 Mbps throughput. In comparison, continuous-wave (CW) communication systems can achieve relatively faster data rates, yet come at a price of high power consumption, not favorable for general power efficiency or mobile applications. The respective digital-to-digital encoding, multiple pulse-width modulation has the potential to provide a substantial transmit power savings conducive for longer battery lifetimes of a mobile system, while maintaining data throughput on the order of Mbps, and can render excellent BER performance.