A Comprehensive Performance Comparison of DFT-S DMT and QAM-DMT in UOWC System in Different Water Environments

In this paper, we experimentally demonstrate a 450-nm laser underwater optical wireless transmission system, in which comprehensive investigation is made to show the significant performance improvement of discrete Fourier transform spread multi-tone (DFT-S DMT) as compared conventional quadrature amplitude modulation (QAM-DMT) modulation. DFT-S DMT outperforms QAM-DMT terms bit error rate (BER) due low peak-to-average-power ratio (PAPR) and capability counteracting high frequency fading band-limited communication (UOWC) system. order avoid signal-to-noise-ratio (SNR) degradation at fringe subcarriers, several zeros are padded edge each block before operation. The experimental results superiority with different water environments, including turbidities, bubbles, flow. Data rates ~16.16 Gbps ~13.96 BER 3.8 × 10 -3 achieved by 16-QAM 16-QAM-DMT over 5-m channel, respectively, indicates that capacity enhancement ~2.2 obtained DMT. Meanwhile, 3-dB receiver sensitivity can always be tested distances. Combined adaptive bit-power loading, 20.04 “clear ocean” channel single diode (LD) demonstrated. For 35-m link, distance-data product reaches 498.4 Gbps*m. To best our knowledge, both data largest among all reported for visible LD. Aimed high-speed deep ocean applications, studies promising future UOWC research.