QSDC model (IMAGE) Advanced Devices & Instrumentation Caption The characteristics of the free-space channel and their effects on optical signal transmission. SNR, signal-to-noise ratio. Credit Advanced Devices & Instrumentation Usage Restrictions News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.