Underwater laser communication with sloped pulse modulation in turbid water

Underwater collaborative work between small mobile platforms (SMP) such as divers, litter submarine or AUV, requires a high data rate communication system which is compact, reliable, affordable and eye-safe. The high bandwidth of LED-based underwater wireless optical communication (UWOC) is an advantage. Artificial, emulated as well as simulated, turbid underwater channel has been studied recently, but no practical nature water. To fully meet the requirements of challenging turbid underwater channel scenarios for SMP, we demonstrated a green LED-based UWOC system up to a bandwidth of 3.4 MHz in a highlyturbid nature lake water. Through a contrast wireless optical communication (WOC) experiment in air, turbid water channel is observed to compensates the receiving signal amplitude attenuates after propagating a longer attenuation length due to multiple-scattered light caused diffusion, and thus to be more like a singleinput multi-output (SIMO) system. From our experimental observation, the SIMO channel model could be employed not only in turbulent UWOC, but also in highly turbid UWOC. Moreover, turbid water channel is observed a ''frequency selection'' effect, thus LED with lower threshold voltage at higher frequency would optimize bandwidth and link range, and a robust pre-code for interference cancellation would be a well-direct choice to constructing different UWOC system in highly turbid water for SMP. Our finding will provide a new reference complementing the current LED-based UWOC systems in realistic water environment.INDEX TERMS Underwater wireless optical communication, channel, turbid water, LED, wireless optical communication, single-input multi-output, visible light communication, small mobile platform. I. INTRODUCTIONUnderwater collaborative work between underwater small mobile platforms (SMP) such as divers, litter submarines or AUV, requires real-time and high data rate link for voice, data or video communication. AUV needs high-speed transmitting link to efficiently collect large amounts of data stored by underwater sensors [1]. Due to the small load capacity and limited power supply, SMP require these high data rate communication system to be compact, simple, reliable and affordable. It is often impractical to make a optical fiber connection between these underwater SMP, the high bandwidth of UWOC is an advantage.The associate editor coordinating the review of this manuscript and approving it for publication was Qunbi Zhuge .

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LED-Based Underwater Wireless Optical Communication for Small Mobile Platforms: Experimental Channel Study in Highly-Turbid Lake Water

Wei

Zhang

et al. 2020

IEEE Access

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Light transmission characteristic analyses of a laser screen in clear water based on the Monte Carlo method

Wang

Hui

et al. 2020

Appl. Opt.

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In order to optimize the design of underwater light screens, the transmission process of the light beam in water is analyzed with the Monte Carlo method. The trajectories and power attenuation of emitted photons, propagating in different types of water from the light source towards the receiver with different initial light powers and transmission distances, are simulated and calculated. The output power can then be obtained to calculate the transmission ratio quantitatively. According to the simulated data, by using the curving fitting method, the exact expression of transmission ratio is derived, which is in the same form as the Beer–Lambert–Bouguer law. Meanwhile, experiments are conducted in a light screen with a vertical line beam laser in clear water to verify the simulations. The experimental results are in agreement with the simulated results, and the differences between them are within ± 0.04 . The presented results give insight into the design of underwater laser screens.

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Underwater laser communication with sloped pulse modulation in turbid water

Cited by 2 publications

References 34 publications

LED-Based Underwater Wireless Optical Communication for Small Mobile Platforms: Experimental Channel Study in Highly-Turbid Lake Water

LED-Based Underwater Wireless Optical Communication for Small Mobile Platforms: Experimental Channel Study in Highly-Turbid Lake Water

Light transmission characteristic analyses of a laser screen in clear water based on the Monte Carlo method

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