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Measurements of optical underwater turbulence under controlled conditions

: Kanaev, A.V.; Gladysz, Szymon; Almeida de Sá Barros, Rui; Matt, S.; Nootz, G.; Josset, D.B.; Hou, W.


Hou, W.W. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Ocean Sensing and Monitoring VIII : 19-20 April 2016, Baltimore, Maryland, United States
Bellingham, WA: SPIE, 2016 (Proceedings of SPIE 9827)
ISBN: 978-1-5106-0068-3
Paper 982705, 8 pp.
Conference "Ocean Sensing and Monitoring" <8, 2016, Baltimore/Md.>
Conference Paper
Fraunhofer IOSB ()
underwater light propagation; wavefront sensing; power spectrum

Laser beam propagation underwater is becoming an important research topic because of high demand for its potential applications. Namely, ability to image underwater at long distances is highly desired for scientific and military purposes, including submarine awareness, diver visibility, and mine detection. Optical communication in the ocean can provide covert data transmission with much higher rates than that available with acoustic techniques, and it is now desired for certain military and scientific applications that involve sending large quantities of data. Unfortunately underwater environment presents serious challenges for propagation of laser beams. Even in clean ocean water, the extinction due to absorption and scattering theoretically limit the useful range to few attenuation lengths. However, extending the laser light propagation range to the theoretical limit leads to significant beam distortions due to optical underwater turbulence. Experiments show that the magnitude of the distortions that are caused by water temperature and salinity fluctuations can significantly exceed the magnitude of the beam distortions due to atmospheric turbulence even for relatively short propagation distances. We are presenting direct measurements of optical underwater turbulence in controlled conditions of laboratory water tank using two separate techniques involving wavefront sensor and LED array. These independent approaches will enable development of underwater turbulence power spectrum model based directly on the spatial domain measurements and will lead to accurate predictions of underwater beam propagation.