| 1. |
- Fei, Chao, et al.
(author)
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Demonstration of 15-M 7.33-Gb/s 450-nm Underwater Wireless Optical Discrete Multitone Transmission Using Post Nonlinear Equalization
- 2018
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In: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 36:3, s. 728-734
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Journal article (peer-reviewed)abstract
- In this paper, we experimentally demonstrate an underwater wireless optical communication (UWOC) system using a 450-nm gallium nitride (GaN) laser and adaptive bit-power loading discrete multitone (DMT). To enhance the system capacity, a post nonlinear equalizer based on the simplified Volterra series is employed at the receiver to mitigate the nonlinear impairments of the UWOC system. By combining the adaptive bit-power loading with nonlinear equalization, 7.33-Gb/s DMT-modulated UWOC under 15-m tap water is achieved at a bit error rate below the 7% hard-decision forward error correction (FEC) limit 3.8 x 10(-3). The electrical signal bandwidth is 1.25 GHz, which corresponds to an electrical spectrum efficiency of similar to 6 bit/s/Hz. The capacity-distance product reaches 109.95 Gb/s-m in a single channel UWOC system with tap water. Compared with the linear equalization case, the system capacity at the FEC limit for 15-m underwater transmission is improved by similar to 18% with the nonlinear equalization. Furthermore, the impact of turbidity on the performance of UWOC system is investigated by measuring the signal-to-noise ratio (SNR) under different suspension concentrations of Al(OH)(3) and Mg(OH)(2). The results show that significant SNR gains (>3 dB for transmission distance up to 11 m) can be obtained by the nonlinear equalization over a wide range of water turbidity levels representing "clear ocean," "coastal ocean," and "harbor water," which demonstrates the robustness of the proposed scheme in various ocean environments.
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| 2. |
- Fei, Chao, et al.
(author)
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16.6 Gbps data rate for underwater wireless optical transmission with single laser diode achieved with discrete multi-tone and post nonlinear equalization
- 2018
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In: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 26:26, s. 34060-34069
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Journal article (peer-reviewed)abstract
- In this paper, we experimentally demonstrate a 450-nm laser underwater wireless optical transmission system by using adaptive bit-power loading discrete multi-tone (DMT) and Volterra series based post nonlinear equalization. Post nonlinear equalization mitigates the nonlinear impairment of the UWOC system. By incorporating post nonlinear equalization with a 3rd-order diagonal plane kernel, the received signal-to-noise ratio (SNR) can be improved by similar to 2 dB compared with a linear equalization method. The measured transmission capacity of the UWOC system is 16.6 Gbps over 5 m, 13.2 Gbps over 35 m, and 6.6 Gbps over 55 m tap water channel, with bit error rates (BERs) below the standard hard-decision forward error correction (HD-FEC) limit of 3.8 x 10(-3). The used electrical signal bandwidth is 2.75 GHz, corresponding to electrical spectrum efficiency of similar to 6 bit/s/Hz. The distance-datarate product reaches 462 Gbps*m at 35 m tap water transmission. To the best of our knowledge, both the data rate and distance-data rate product are the largest reported for single laser diode.
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