150 m/500 Mbps Underwater Wireless Optical Communication Enabled by Sensitive Detection and the Combination of Receiver-Side Partial Response Shaping and TCM Technology

Abstract

In this paper, a joint digital signal processing (DSP) scheme including partial response shaping and trellis coded modulation (TCM) technology is proposed to mitigate the bandwidth limitation of the long-reach underwater wireless optical communication (UWOC) system. The similarity of spectral responses between the partial response filter and the communication system is utilized to suppress the enhancement of noise and distortion induced by the full-response feed-forward equalizer. A random interleaver and a precoder are applied to whiten the noise and distortion. In a laboratory experiment, the minimal required received optical power of -29.8 dBm (at a BER of 3.80 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> - 3</sup> ) is realized at a data rate of 500 Mbps. In a standard swimming pool, the proposed system successfully achieves a data rate of 500 Mbps with a transmission distance up to 150 m, at which the total attenuation is measured to be 53.47 dB. Such a data rate, enabled by the proposed joint DSP scheme, is 8.0%, 9.2%, and 14.2% higher than those achieved by solely using partial response shaping scheme, TCM scheme, and least square equalization scheme, respectively. To the best of our knowledge, this is the first time to employ the combination of partial response shaping and TCM technology in UWOC for high-speed long-reach transmission.