Loss on space-ground laser communication downlinks due to optical turbulence: results from wave-optics simulations

This paper presents the results of wave-optics simulations predicting losses due to the effects of atmospheric optical turbulence on laser communication (lasercom) space-to-ground downlinks. Power in the aperture, tilt-corrected Strehl, and phase-corrected Strehl are reported. These may be used by engineers evaluating design trades and developing link budgets. Results are reported for a variety of scenarios at both the 1.55 and 1.06 μm lasercom bands. Zenith angles from 0 to 80 deg and aperture diameters of 0.1 to 1.0 m are modeled. Height of the receiver's aperture above ground is considered and found to make only a small difference in link turbulence loss. Both 1 and 3 times the well-known Hufnagel-Valley 5/7 turbulence profile are used in the simulations. For each scenario, 4800 statistically independent instances were run. This paper reports the results of the cumulative probability tails of fade at 2.5×10−3. On links where errors are dominated by turbulence-induced fades, with proper interleaving and a good forward error correction code, this probability of channel fade can translate to a user bit error rate orders of magnitude lower.