The integrity of a free-space optical communications link can be directly correlated to the atmospheric conditions through which the link is made. The link may become degraded due to optical turbulence and absorptive/ scattering losses resulting in reduced signal strength and may result in failure to close a link. It is important to analyze atmospheric conditions in order to predict and mitigate these performance losses. The goal of this work is to characterize local atmospheric conditions in a coastal environment over a 560 m terrestrial optical range. Local atmospheric and weather data were gathered utilizing several data collection instruments including an anemometer, a scintillometer, and a weather station hub. The data analyzed in this work were temperature and path averaged scintillation index (Cn2). Experimental data collections and analysis of monthly weather conditions are presented with Cn2 values ranging from 10-15 to 10-12 (m-2/3) and temperature values ranging from 8 to 31 (℃).
Current Free Space Optical Communications (FSOC) technologies require Direct Line of Sight (DLoS) between two users. In a dynamic environment where users are distributed across the battlespace, reestablishing DLoS links between multiple users becomes challenging; hence, easing the harsh Line of Sight (LoS) requirement may make FSOC more accessible to these types of environments. Our on-going FSOC research has identified Indirect Line-of-Sight (ILoS) optical physical layer approaches that enable a novel Multi Access Tactical Optical Communications (MATOC) network layer while maintaining many of the benefits offered by a LoS system. In this paper the authors will summarize successful experiments in one physical layer approach, diffuse reflection. Further experimentation beyond the timeline of this conference is underway and will be included in future publication(s).
Enhancements to rapidly tunable photon orbital angular momentum (OAM) states have opened the door to enhancing free space optical applications across various domains. Photon OAM states have been proven to identify preferential optical transmission channels (eigenchannels) that reduce the impact of turbulent media on free space optical links. In this study, we initiate the use of photon OAM-induced preferential optical transmission channels to enhance the detection and sensing of concealed objects by investigating experimental thrusts into non-electronic feedback mechanisms such as diffuse scattering. This technology leverages the compact, rapidly tunable OAM generator technology developed by researchers at Clemson University to identify these preferential channels and take advantage of them to demonstrate improvements in detectability over traditional lasing techniques. In this work, we detail forthcoming experiments between NIWC Atlantic and Clemson that are focused on investigating this issue, which will enable future experimentation and research into the enhancement of detecting concealed objects among other remote sensing applications.
Free space optical communications are highly dependent on atmospheric conditions to ensure successful transmission from transmitter to receiver. The integrity of an optical communications link can degrade depending on the atmospheric conditions during propagation. This reduced signal strength of an optical communications link can be directly associated with atmospheric conditions that cause scattering, absorption, and optical turbulence. Our main goal is to characterize the atmosphere for modeling and analysis of atmospheric conditions for optimizing optical communications in a coastal environment. Instruments including an anemometer, scintillometer, and a weather station hub collected local atmospheric and weather data. These data generated plots describing temperature, wind speed and direction, humidity, pressure, and path averaged scintillation index throughout the seasons. We began analyzing the path averaged scintillation index against the other data points to identify trends and correlations in the path averaged scintillation index and how it is affected by the other atmospheric conditions.
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