Performance analysis of an adaptive optics system for free-space optics communication through atmospheric turbulence

Abstract

The performance of free-space optics communication (FSOC) is greatly degraded by atmospheric turbulence. Adaptive optics (AO) is an effective method for attenuating the influence. In this paper, the influence of the spatial and temporal characteristics of turbulence on the performance of AO in a FSOC system is investigated. Based on the Greenwood frequency (GF) and the ratio of receiver aperture diameter to atmospheric coherent length (D/r0), the relationship between FSOC performance (CE) and AO parameters (corrected Zernike modes number and bandwidth) is derived for the first time. Then, simulations and experiments are conducted to analyze the influence of AO parameters on FSOC performance under different GF and D/r0. The simulation and experimental results show that, for common turbulence conditions, the number of corrected Zernike modes can be fixed at 35 and the bandwidth of the AO system should be larger than the GF. Measurements of the bit error rate (BER) for moderate turbulence conditions (D/r0 = 10, fG = 60 Hz) show that when the bandwidth is two times that of GF, the average BER is decreased by two orders of magnitude compared with fG/f3dB = 1. These results and conclusions can provide important guidance in the design of an AO system for FSOC.

Experimental Study of the Free Space Optics Communication System Operating in the 8–12 µm Spectral Range

“…On the other hand, in Reference [45] the influence of spatial and temporal characteristics of atmospheric turbulence was analyzed. It turned out that temporal characteristics were slightly stronger than spatial ones.…”

Turbulence-Resistant FSO Communication Using a Few-Mode Pre-Amplified Receiver

“…1, a lens is used to focus the free-space beam onto the facet of the fiber, and the focal length of the lens or the magnification of the imaging system affects the coupling efficiency 24 . For coupling a uniform field into the fiber, an optimum magnification can be calculated 4 , which was adopted when simulating the performance of AO. When the turbulence level increases, the number of spatial modes contained in the distorted wavefront and in the receiving FMF also increase.…”

“…Unfortunately, atmospheric turbulence distorts the wavefront, resulting in spatiotemporal amplitude and phase fluctuations at the detector 3 . Current FSO communication is dominated by the use of adaptive optics (AO) to correct wavefront distortions 4,5 , followed by single-mode (SM) optically pre-amplified receivers, as shown in Fig. 1(a).…”

Historical perspective of free space optical communications: from the early dates to today's developments

“…There are application limitations in WFSbased wavefront aberration measurement technique particularly in the multiphoton microscope for biological imaging and FSO communications along with distributed turbulence optical path [55,56]. To solve this limitation, WFS-less AO systems are introduced and found more suitable for all applications [55][56][57]. Today's AO system attracts much attention to model-based and model-free correction techniques.…”

“…6. More details on various control techniques of wavefront aberration measurement, control algorithms, and wavefront corrections are available in [27,[52][53][54][55][56][57]. High speed wavefront distortion measurement and higher real-time performance in correcting is very important especially for FSO communication since the data rate is high.…”