40 Gbps High-Speed Free-Space Inter-Island Optical Communication Over 29 Kilometers Under Turbulent Near-Sea Surface Environment

Free-space optical (FSO) communication has attracted considerable research interests in the past decade. Compared with vertical FSO links, near-sea long-distance FSO horizontal links are exposed to stronger atmospheric turbulence, and it is a quite challenging to extend the communication distance under this scenario. In this study, we firstly propose a high-speed low-cost near-sea surface FSO communication scheme between two islands located by 29 kilometers apart. In this scheme, a maximum communication rate of 40 Gbps can be achieved by employing commercially available SFP+ packaged optical modules with data rate of 2.5/10 Gbps as the transmitters in combination with 4-wavelength dense wavelength division multiplexing technology. Additionally, high-power transmission and large-aperture reception techniques are exploited to suppress the attenuation effects and atmospheric turbulence. Experimental results show that a bit error rate of 1 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> and an averaged receiving optical power of −19 dBm can be obtained under a scintillation index of 0.21. Our proposed FSO communication scheme provides competitive solutions for transmitting information via near-sea surface channels between islands.