NICOP - Turbulence compensation for atmospheric and underwater environments
Abstract
Turbulence compensation for atmospheric and underwater environments:Background and RelevanceMany Navy applications that involve passive or ladar imaging, optical communications, and high energy lasers (HEL) are subject to various degradation effects along propagation paths. In particular, refractive index inhomogeneities along the path can cause deviation, spread, jitter, and/or decoherence in laser beams, and introduce distortions in the observed optical wavefront. This path degradation which the optical science community calls "turbulence" is not necessarily related to fluid flow turbulence, and can occur both underwater and in the air. Refractive index inhomogeneities in air are caused by temperature fluctuations, while in water they can be caused by both temperature and salinity variations. Optical path turbulence can reduce the effective operational range of imaging, communication, and HEL systems, undermine the spatial and temporal resolution of imagers, and increase the error rates of optical communication channels. In advanced applications, effects of turbulence can be mitigated with wavefront correction systems using adaptive optics based on an accurate model of the path turbulence affecting the particular observation. Underwater optical turbulence is not represented accurately by existing models and comprehensive studies are needed to characterize turbulence and predict the performance of underwater imaging and optical communication systems in diverse operational environments. Although optical turbulence in air has been studied for decades, recent observations and developments have spurred significant analytical advances toward more accurate models. The emerging analytical models need to be studied to determine their contributions to relevant operational settings, especially to predict the effectiveness of free space optical communication systems with and without wavefront correction. Optical turbulence in air is of interest to both ONR and EOARD. Innovation1) This project will develop a high-fidelity model of underwater optical turbulence and validate it using experimental data collected previously in NRL~s controlled turbulence water tank at the Stennis Space Center facility.2) The new turbulence model and Fraunhofer Institute s scattering and absorption models will be integrated in a comprehensive simulation which will be used to study underwater optical path phenomena in collaboration with NRL scientists who are developing advanced underwater laser imaging systems. 3) The PI will investigate techniques for reducing the error rates of optical communication systems in air, using adaptive optics and advanced models of atmospheric optical turbulence. 4) The performance of a new optical communication method, Orbital Angular Momentum (OAM), will be characterized with and without adaptive optics. ONR and EOARD ConnectionUnderwater imaging is an active area of research in NRL, supported by Ravi Athale in Code 31. Dr. Athale is especially interested in the study of turbulence as it affects the performance of most passive and active EO/IR systems underwater and in air. Advanced turbulence models can also contribute to the study of HEL propagation and effectiveness which is of interest to Frank Peterkin and Peter Morrison in Code 35.The Air Force and EOARD have expressed very strong interest in the study of turbulence in air in relation to long-range optical communication systems based on ground, air and space platforms. EOARD has committed $150,000 per year to co-fund all three years of this project. Desired OutcomesA high-fidelity model of optical turbulence underwater and in air. A simulation component delivered to NRL, to reproduce underwater turbulence effects accurately. A comprehensive study of adaptive optics wavefront correction for underwater imaging and optical communications in air. Close collaboration with NRL and AFRL scientists. Peer reviewed publications. PIThe PI, Dr. Szymon Gladysz is head of the A
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 03, 2017
- Source ID
- N629091712037
Entities
People
- Szymon Gladysz
Organizations
- Office of Naval Research
- United States Navy