200-m/500-Mbps underwater wireless optical communication system utilizing a sparse nonlinear equalizer with a variable step size generalized orthogonal matching pursuit

Abstract

Linear and nonlinear impairments in underwater wireless optical communication (UWOC) systems caused by the limited bandwidth and nonlinearity of devices severely degrade the system performance. In this paper, we propose a sparse Volterra series model-based nonlinear post equalizer with greedy algorithms to mitigate the nonlinear impairments and the inter-symbol interference (ISI) in a UWOC system. A variable step size generalized orthogonal matching pursuit (VSgOMP) algorithm that combines generalized orthogonal matching pursuit (gOMP) and adaptive step size method is proposed and employed to compress the Volterra equalizer with low computational cost. A maximum data rate of 500 Mbps is realized with the received optical power of −32.5 dBm in a 7-m water tank. In a 50-m swimming pool, a data rate of 500 Mbps over 200-m underwater transmission is achieved with a BER lower than the forward error correction (FEC) threshold of 3.8 × 10−3. The number of kernels of the sparse Volterra equalizer is reduced to 70% of that of the traditional Volterra equalizer without significant BER performance degradation. Compared with orthogonal matching pursuit (OMP) scheme and regularized orthogonal match pursuit (ROMP) scheme, the VSgOMP scheme reduces the running time by 68.6% and 29.2%, respectively. To the best of our knowledge, this is the first time that a sparse Volterra equalizer combined with VSgOMP algorithm is employed for the nonlinear equalization in a long-distance high-speed UWOC system.

50 m/187.5 Mbit/s real-time underwater wireless optical communication based on optical superimposition

“…Underwater wireless optical communication (UWOC) has the advantages of high data rate and low latency, but with the shortcomings of strict link alignment and limited transmission distance [1][2][3][4] . The blue laser diode (LD), with high power, is gradually becoming the mainstream as the light source in the long-distance UWOC system [5][6][7][8][9][10] . Besides, many researchers employed high-sensitivity optical detectors such as a multi-pixel photon counter (MPPC), single-photon avalanche diode (SPAD), and photomultiplier tube (PMT) as receivers to detect weak optical signals [6][7][8][9][10][11] .…”

“…The blue laser diode (LD), with high power, is gradually becoming the mainstream as the light source in the long-distance UWOC system [5][6][7][8][9][10] . Besides, many researchers employed high-sensitivity optical detectors such as a multi-pixel photon counter (MPPC), single-photon avalanche diode (SPAD), and photomultiplier tube (PMT) as receivers to detect weak optical signals [6][7][8][9][10][11] .…”

“…In the same year, a joint DSP scheme including partial response shaping and trellis-coded modulation technology was proposed and employed in a UWOC system, which successfully achieved a data rate of 500 Mbit/s with a transmission distance up to 150 m [8] . Besides, the sparse Volterra equalizer, which can effectively reduce the computational complexity, was developed for the UWOC system to realize a data rate of 500 Mbit/s in a 200 m underwater transmission [9] . Recently, a wideband PMT-based UWOC system was proposed, in which the transmission distance and data rate were pushed to 100.6 m and 3 Gbit/s, respectively [10] .…”

Real-Time Optical-Wireless Video Surveillance System for High Visual-Fidelity Underwater Monitoring

“…However, tethering significantly constrains the maneuverability and working range of the ROVs. In recent years, with the advancement of semiconductor and digital signal processing technologies, underwater wireless optical communication (UWOC) technology with high bandwidth and low latency has made tremendous progress in terms of data rates (up to ~Gbit/s) and transmission distances (up to hundreds of meters) [7][8][9]. It proved to be a promising technology in overcoming the limitations of conventional underwater acoustic communication for high-resolution multimedia streaming in the > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 2 order of Mbit/s across short transmission ranges (less than ~100 m) [10][11][12][13][14][15][16][17][18][19][20][21].…”

Water-Wave Effect on the Encryption and Deep-Learning-Based Recognition of a Speech Signal Transmitted Over a Wireless Optical Communication Channel

“…NDERWATER wireless optical communication (UWOC) has attracted a lot of interest recently due to the emergence of Internet of Underwater Things (IoUT) [1] and to an increase in utilization of autonomous underwater vehicles (AUVs) for exploration of seas and oceans [2]. As a result of the requirements for fast, reliable and secure UWOC, this field continues to evolve in attempt to reach data rates of tens of Gbps [3], distances of hundreds of meters [4], and high signal sensitivities [5]. Additional research directions in the field of UWOC include advanced multiplexing techniques based on orbital angular momentum [6] for increased channel capacity [7], effects of turbulence on communication quality [8], and use of advanced optical sources for high speed UWOC [9].…”