Abstract
In this paper, an effective method of underwater coherent optical wireless communication (UCOWC) with a simplified detection scheme is proposed. The proof-of-concept experiments with M-ary PSK have been conducted with a common laser used for the signal source and local oscillator (LO). The BER performance has been evaluated at different underwater channel attenuations and the maximum achievable attenuation length (AL) with a BER below the forward error correction (FEC) limit of 3.8×10-3 is investigated. The tested system offers data rates of 500 Mbps, 1 Gbps, and 1.5 Gbps with the BPSK, QPSK and 8PSK modulated signals, respectively. The corresponding maximum achievable attenuation lengths are measured as 13.4 AL 12.5 AL, and 10.7 AL. In addition, the performance degradation of the practical system with separate free running lasers for the signal and LO is also estimated. To the best of our knowledge, the UCOWC system is proposed and experimentally studied for the first time. This work provides a simple and effective approach to take advantages of coherent detection in underwater wireless optical communication, opening a promising path toward the development of practical UCOWC with next-generation underwater data transmission requirements on the capacity and transmission distance.
Highlights
Underwater wireless communication (UWC) plays a significant role in the underwater environment exploration, which has never been stopped and has gained a growing interest in recent years [1]
By using M-ary phase shift keying (PSK) modulation formats, the feasibility of the underwater coherent wireless optical communication (UCOWC) is experimentally demonstrated, which would open the door toward designing the generation underwater optical wireless communication (UWOC) system with higher data rate and better sensitivity
The experimental measurements are conducted via block by block data transfer from an oscilloscope to a computer, and each constellation diagram corresponds to a collection of 214 samples
Summary
Underwater wireless communication (UWC) plays a significant role in the underwater environment exploration, which has never been stopped and has gained a growing interest in recent years [1]. Full information can be restored on both In-phase (I) and Quadrature (Q) components of the complex amplitude of optical electric field [12,13,14] It can provide an additional degree of freedom available for encoding of information in UWOC and offer higher spectral efficiency compared to IM-DD systems [11,15]. The other advantages of the use of coherent receiver over IM-DD systems are the higher receiver sensitivity due to the strong optical field of LO and better tolerance to background noise [11,16,17]. By using M-ary PSK modulation formats, the feasibility of the underwater coherent wireless optical communication (UCOWC) is experimentally demonstrated, which would open the door toward designing the generation UWOC system with higher data rate and better sensitivity.
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