30 August 2017 Hemispherical optical dome for underwater communication
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Abstract
For many years, acoustic systems have been used as the primary method for underwater communication; however, the data transfer rate of such systems is low because sound propagates slowly through water. A higher throughput can be achieved using visible light to transmit data underwater. The first issue with this approach is that there is generally a large loss of the light signal due to scattering and absorption in water, even though there is an optimal wavelength for transmission in the blue or green wavelengths of the visible spectrum. The second issue is that a simple communication system, consisting only of a highly directional source/transmitter and small optical detector/receiver, has a very narrow field of view. The goal of this project is to improve an optical, underwater communication system by increasing the effective field of view of the receiving optics.

To this end, we make two changes to the simple system: (1) An optical dome was added near the receiver. An array of lenses is placed radially on the surface of the dome, reminiscent of the compound eye of an insect. The lenses make the source and detector planes conjugate, and each lens adds a new region of the source plane to the instrument's total field of view. (2) The receiver was expanded to include multiple photodiodes. With these two changes, the receiver has much more tolerance to misalignments (in position and angle) of the transmitter.

Two versions of the optical dome (with 6" and 8" diameters) were designed using PTC’s Creo CAD software and modeled using Synopsys' CODE V optical design software. A series of these transparent hemispherical domes, with both design diameters, were manufactured using a 5-axis mill. The prototype was then retrofitted with lenses and compared with the computer-generated model to demonstrate the effectiveness of this solution. This work shows that the dome design improves the optical field of view of the underwater communication system considerably. Furthermore, with the experimental test results, a geometric optimization model was derived providing insights to the design performance limits.
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ron S. Shiri, Ron S. Shiri, Emily L. Lunde, Emily L. Lunde, Patrick L. Coronado, Patrick L. Coronado, Manuel A. Quijada, Manuel A. Quijada, } "Hemispherical optical dome for underwater communication", Proc. SPIE 10408, Laser Communication and Propagation through the Atmosphere and Oceans VI, 1040810 (30 August 2017); doi: 10.1117/12.2274100; https://doi.org/10.1117/12.2274100
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