Low-cost Underwater Wireless Optical Communication System For Small Facilities

In the21st century, human take great efforts to the research and development of the sea, promoting the relative technology is also demanded. Conditions of Underwater and land-based environment differ greatly, so quite a lot of land-based technologies can’t be applied in underwater environment. Underwater communication is an important technology for marine and underwater development and exploration. Unlike the terrestrial and space communications, underwater communication is mainly in freshwater seawater. Existing technology can achieve freedom communications in the land and space communications, but for the realization of the underwater communication, it is quite difficult. Traditional underwater communication is divided into wired and wireless communications; underwater cable communication is achieved through the laying of submarine cables. Because the electromagnetic waves have a great attenuation in the water, communications with electromagnetic waves in the underwater is almost impossible. Underwater wireless communication using underwater acoustic communication technology is the most mature technology of wireless communication in underwater target. However, the acoustic waves in the water greatly attenuated, and the attenuation is proportional to the square of the acoustic frequency. Therefore, the propagation speed of underwater acoustic communication technology, is slow, acoustic equipment is bulky, and the cost is huge. It can’t meet the small-volume and low-cost requirements for underwater communication applications.In this paper, based on the analysis of the status of current underwater communication technology and the good water permeability of blue-green light, a low-cost wireless optical communication device is designed.-Compared with traditional means of communication, underwater wireless optical communication in this paper has large data capacity, high bandwidth, fast transfer rate, light volume weight, safety, security performance and low cost.The main content of this paper is as follows: (1) Technical means and the development status of the current underwater communication at home and abroad is described, and the strengths and weaknesses of the various technical are elaborated.(2) The optical characteristics of the water is studied, the transmission characteristics of the green indicator parameters in the fixed water is analysed. Taking into account the dissipation loss and optical loss of the beam expander, a communication link model of optical underwater transmission effect of the channel is proposed.(3) A low cost underwater wireless optical communication apparatus is designed, the apparatus include a green light source, an optical modulator drive unit, a control and display unit, a photodiode, and a photoelectric conversion unit. The apparatus can realize underwater close-high-speed information transmission.The main features of this paper or innovations are as follows:(1) Combined with the wireless space laser communication technology and existing underwater communication method, an optical wireless communication technology for underwater close-information transmission is proposed.(2) The design of low-cost wireless optical communication devices, has the advantages of low cost, small size, high bandwidth, low power consumption and suitable for short distance data transmission occasions in the underwater environment.(3) Through laboratory experiments, the relationships of light luminous power, the scattering angle and the sensitivity of the photo-detector are demonstrated. Analyze the underwater optical wireless communication quality, that is mainly about the SNR and BER of different equipments and modulation way.