90-m/560-Mbps underwater wireless optical communication utilizing subband multiple-mode full permutation CAP combined with an SNR-weighted detector and multi-channel DFE.

In this paper, a joint signal processing scheme including a subband multiple-mode full permutation carrierless amplitude phase modulation (SMMP-CAP), signal-to-noise ratio weighted detector (SNR-WD), and multi-channel decision feedback equalizer (MC-DFE) is proposed to mitigate the bandwidth limitation of a high-speed long-reach underwater wireless optical communication (UWOC) system. Referring to the trellis coded modulation (TCM) subset division strategy, 16 quadrature amplitude modulation (QAM) mapping set is divided into four 4-QAM mapping subsets by SMMP-CAP scheme. An SNR-WD and an MC-DFE are employed to enhance the demodulation effect of this system in a fading channel. In a laboratory experiment, the minimal required received optical powers (ROPs) for data rates of 480 Mbps, 600 Mbps, and 720 Mbps, at hard-decision forward error correction (HD-FEC) threshold of 3.80 × 10