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Shimadzu Review 79[3・4] (2022)
This article describes the development of the MC500 underwater optical wireless modem. The MC500 is principally a data communication device that provides an online, bi-directional connection between underwater vehicles and surface vessels. Underwater vehicles have primarily been operated remotely via cables that provide both power and communication, but these cables create resistance in water that reduces the mobility of the underwater vehicle. Accidents involving disconnection of these cables are also a frequent occurrence. These shortcomings have led to increased interest in the development of battery-driven underwater vehicles and wireless means of data communication. Sound is known to propagate well underwater, with whale vocalization a well-known example of sound used as a means of underwater communication. This phenomenon has been used to develop sound-based underwater communication technology, with sound currently an accepted means of underwater communication. However, while attempts have been made to increase the speed of underwater acoustic communication, the presence of underwater noise, the Doppler effect, and other factors have prevented a speed increase sufficient for stable video transmission. Visible light waves undergo minimal attenuation in seawater, and underwater optical wireless communication based on visible light is now attracting interest as a high-speed means of underwater communication. Because underwater optical wireless communication uses water as a transmission medium, technological development in this field must first address how light is attenuated in water and calculate light attenuation rates for the range of conditions encountered in nature. Herein is described a course of development that addresses these issues, the key performance specifications of the resulting MC500, and details of future product development.
Magnetic Systems Department, Aircraft Equipment Division, Shimadzu Corporation, Kyoto, Japan
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