Steering compensation for strong vertical refraction gradients in a long-distance free-space optical communication link over water

M. R. Suite, C. I. Moore, H. R. BurrisJr., L. Wasiczko, M. F. Stell, W. S. Rabinovich, W. J. Scharpf, G. C. Gilbreath, David G. Voelz, Jennifer C. Ricklin
2005 Free-Space Laser Communications V  
It is important to be able to characterize and compensate for refraction effects in free-space optical laser communication (FSO lasercom). The refractive index depends on various properties of the propagation medium such as temperature, pressure, and moisture, with temperature having the largest affect. Very strong but slow-varying thermal gradients have been observed at the NRL Chesapeake Bay lasercom testbed, which offers a 16 km one-way (32 km round-trip) FSO lasercom link over water.
more » ... over water. Thermal gradients affect the elevation-pointing angle, and their magnitudes are a function of the time of day and year and also the weather conditions. These vertical refraction errors are corrected by the use of a fiber positioner controlled by a position-sensing detector (PSD). This system is implemented into the receiver at the NRL Chesapeake Bay lasercom testbed. System test results will be presented.
doi:10.1117/12.622394 fatcat:5qo5srk5ybamri2hw6jvorsuhy