Investigation of Underwater Wireless Optical Communications Links With Surface Currents and Tides for Oceanic Signal Transmission

Zhijian Lv,Zhaojun Liu,Chengfeng Qiu,Gui He

doi:10.1109/jphot.2021.3076895

Abstract

This report investigated underwater wireless optical communication (UWOC) links in the presence of surface currents and tides. The scenario of surface currents and tides was generated by a sea water tank, a water pipe, and a water pump of different flow rates. It built the oceanic channel of UWOC varied with the salinity and flow rate in the UWOC transmission. The data rate of UWOC links based on a 520-nm laser diode and none-return-to-zero on-off keying (NRZ-OOK) modulation can achieve 3.4 Gb/s at a bit error rate (BER) of 3.78 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\times 10^{-4}$</tex-math></inline-formula> in 1.8 m long sea water tank when a flow rate reached 1.08 m/s. The BER, eye-diagrams, and received signal optical power measurements showed that both the increasing salinity and flow rate cause the UWOC channel attenuation, thus degrade the performance of UWOC links.

Highlights

Demands for high speed, large bandwidth underwater data communication links are growing to meet the explosive underwater human activities
When a small signal is modulated to the direct current, it would result in the optical power variation of the laser diodes (LDs)
We firstly experimentally demonstrated the salinity and flow rate induced turbulence employing to the high-speed underwater wireless optical communication (UWOC) links by using 520-nm LD and OOK modulation scheme

Summary

Introduction

Demands for high speed, large bandwidth underwater data communication links are growing to meet the explosive underwater human activities. Underwater wireless optical communication (UWOC) links based on laser diodes (LDs) can balance a high data rate up to Gb/s and a moderate transmission range of 100 m [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]. Underwater optical turbulence occurs due to the random variations of the refraction index along the optical path that could arise due to the presence of dissolved and suspended particles in the water It is impacted by the uniformity changed by the water flow. The investigation of UWOC links in the presence of surface currents and tides becomes significant, which could build a more practical scenario of UWOC links in the sea

Experimental Details

Results

Conclusions