The Effect of Weather and Atmosphere on Laser Communication Systems

The purpose of CLARITY – Climatic Laser Analysis Research in Turbulent Yields - is to develop and observe a reliable Laser Communication (LC) system. First developed in 1995, LC is a powerful tool for efficient communication, but LC is also adversely affected by atmospheric factors in applications such as deep space communications. The temperature, humidity, wind turbulence, precipitation, and numerous other environmental factors affect the strength of the signal and therefore the quality of the data or message being transmitted. CLARITY aims to research how different environmental conditions on Earth and other planets affect the data integrity of an LC signal. While some research has been done on various mitigation techniques for the environmental effects, there is no robust method that is able to alleviate all issues at once. CLARITY’s main objective is to gather performance data for various environmental conditions and develop a robust method to strengthen the LC signal to combat environmental conditions it may face. The work done by CLARITY will impact military, private, and commercial applications as the focus on improving signal strength continues and can provide a newfound security and trust in LC that has been absent in recent years. The CLARITY project involves designing and testing both static and mobile laser LC systems to evaluate the impact of various environmental factors. The system development phase includes testing lasers with different wavelengths—red, blue, and green—to analyze how atmospheric conditions affect beam propagation. To establish a reference performance level, baseline tests will be conducted in a vacuum chamber, allowing for a controlled comparison against real-world conditions. Environmental testing is carried out in diverse weather scenarios, including snowfall, high temperatures, rainfall, with a controlled wind tunnel test, to compare and assess signal integrity under varying atmospheric influences. Throughout these experiments, the LC system will use photodiodes, spectrometers, power meters, and atmospheric sensors to measure signal strength, noise levels, and overall transmission reliability. One method to counter the effects of the atmosphere that CLARITY will test is the application of error correction codes (ECC) and modulation techniques that are robust enough to withstand signal degradation. Forward error correction (FEC) schemes, such as Reed-Solomon and convolutional codes, are often used in laser communication to improve the fidelity of the data by updating and repairing the errors introduced during the transmission. Additionally, the new modulation techniques, such as QAM and OFDM, amplify the data rate and minimize the impact of atmospheric disturbances. Beamforming is another technique that has been used to strengthen signals. Beamforming adjusts the phases transmitted by adjacent laser emitters to create a focused beam directed at the receiver. This focused beam increases the signal strength and reduces beam wandering. Beamforming has been demonstrated in several experimental LC systems and has been shown to improve link reliability under adverse atmospheric conditions. Despite the progress in individual mitigation techniques, a holistic approach that addresses all the atmospheric effects simultaneously is still an area of ongoing research. By developing a reliable LC test model, the CLARITY team will be able to experiment with various designs and extrapolate a comprehensive LC model that will enhance the current capabilities laser communication has currently demonstrated. With interest in interplanetary space exploration rising, LC technologies can take advantage of the increased data rates and decreased transmission time has the chance to advance space communication technology. CLARITY’s research into improving data integrity and beam deformation due to environmental conditions will ensure that LC can be effectively used in future space missions.