Measurement of laboratory-simulated atmospheric turbulence by PSD

Atmospheric optical turbulence increases bit error rate and degrades beams quality for wireless laser communication links as laser light propagation in the turbulent atmosphere, and optical turbulence simulation and measurement are important research topics for improving performance of wireless laser communication. An experiment system was built for simulating and measuring optical turbulence for laser propagation experiment. A method based on angle-of-arrival fluctuations of a laser beam through simulated- turbulence is utilized for measuring Fried coherence length (r₀) of optical turbulence. Position sensitive detectors (PSD) have excellent position resolution and are utilized for measuring centroid fluctuations of laser light flux after propagation through laboratory-simulated turbulence in order to offer turbulence parameters required. An instantaneous value of Fried coherence length can be obtained. The simulated turbulence could be 1000 times stronger than that of real atmosphere and Fried coherence length of simulated turbulence spanned from 1.4 to 12cm. The results show that Fried coherence length of laboratory-simulated atmospheric changes very rapidly with time and varies with temperature and wind velocity of the air along the propagation path.