Experimental Demonstration of Underwater Optical Communication Using PPM Modulated 532 nm DPSS Laser
01 Jan 2021-Vol. 258, pp 141-144
TL;DR: In this article, the performance of underwater optical communication (UWOC) link over a distance of ~9 m using a 532 nm DPSS laser modulated with PPM data is evaluated by measuring the bit error rate (BER) for different values of signal-to-noise ratio (SNR).
Abstract: In this paper, we experimentally demonstrate the performance of underwater optical communication (UWOC) link over a distance of ~9 m using a 532 nm DPSS laser modulated with pulse position modulation (PPM) data. The optical PPM signals are received using a Si:PMT-based receiver and the link performance is evaluated by measuring the bit error rate (BER) for different values of signal-to-noise ratio (SNR).We demonstrate 1e-3 BER for optical received power levels as low as—60 dBm (1 nW) with a link loss of ~65 dB.
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TL;DR: To enable high-speed underwater wireless optical communication (UWOC) in tap-water and seawater environments over long distances, a 450-nm blue GaN laser diode directly modulated by pre-leveled 16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data was employed to implement its maximal transmission capacity.
Abstract: To enable high-speed underwater wireless optical communication (UWOC) in tap-water and seawater environments over long distances, a 450-nm blue GaN laser diode (LD) directly modulated by pre-leveled 16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data was employed to implement its maximal transmission capacity of up to 10 Gbps. The proposed UWOC in tap water provided a maximal allowable communication bit rate increase from 5.2 to 12.4 Gbps with the corresponding underwater transmission distance significantly reduced from 10.2 to 1.7 m, exhibiting a bit rate/distance decaying slope of -0.847 Gbps/m. When conducting the same type of UWOC in seawater, light scattering induced by impurities attenuated the blue laser power, thereby degrading the transmission with a slightly higher decay ratio of 0.941 Gbps/m. The blue LD based UWOC enables a 16-QAM OFDM bit rate of up to 7.2 Gbps for transmission in seawater more than 6.8 m.
214 citations
TL;DR: In this article, the effects of wind generated surface waves, associated bubble layer, particulate absorption and scattering, and medium inhomogeneity on the channel characteristics, power budget and channel impulse response of a downlink optical wireless communication (OWC) system using Monte-Carlo numerical simulation technique for two different water types (open-oceanic and coastal).
Abstract: Light propagation in a downlink Optical Wireless Communication (OWC) system from above the sea surface to the underwater medium is influenced by wind generated surface waves, associated bubble layer, particulate absorption and scattering, and medium inhomogeneity. The present study aims to model the combined effects of these factors on the channel characteristics, power budget and channel impulse response of the OWC system using Monte-Carlo numerical simulation technique for two different water types (open-oceanic and coastal). The transmission of light across the air-sea interface is modelled by using a Bidirectional Transmittance Distribution Function (BTDF), whereas the medium inhomogeneity is taken into consideration by stratifying the underwater channel based on the in-situ measured IOPs. In order to examine the effect of stratification, the channel characteristics are estimated by considering the medium as homogenous as well as stratified and compared. Comparison results suggest that the medium stratification provides significant improvement in power estimation in comparison to a case where the medium is considered as homogeneous, for all depths. Similarly, the channel impulse responses estimated for these two conditions are notably different in terms of delay spread, suggesting that the medium stratification in clear and moderately turbid waters may be a vital necessity for precise estimation of channel characteristics. These results will be useful for design and implementation of a physical downlink optical wireless communication system.
19 citations
TL;DR: In this article, the spectral absorption coefficients of particulate (algal and non-algal components) and dissolved substances are modelled and combined with the pure seawater component to determine the total light absorption coefficient of seawater in the Bay of Bengal.
14 citations
01 Jan 2020
TL;DR: In this article, the effects of air-sea interface, bubble and particulate scattering, and medium inhomogeneity on the underwater light field distribution, downwelling irradiance (Ed) was carried out theoretically using Monte Carlo numerical simulation technique.
Abstract: A study of the effects of air–sea interface, bubble and particulate scattering, and medium inhomogeneity on the underwater light field distribution, downwelling irradiance (Ed) was carried out theoretically using Monte Carlo numerical simulation technique. The downwelling irradiance was computed for different scenarios (with and without waves and bubble effects) and compared with the in situ measured values. The wave effect was included according to a model given by Cox and Munk and the effect of bubble was included by estimating the Bidirectional Transmittance Distribution Function (BTDF) of a bubble layer. Furthermore, the effect of the variation of particulate concentration along the vertically downward direction on downwelling irradiance was studied by stratifying the underwater medium, instead of considering homogeneous water column, for the calculation of Ed. The findings showed the importance of considering the air–sea interface (wave and bubble) effects and stratification in estimating the underwater light field distribution and thereby the channel characteristics of an Underwater Wireless Optical Communication (UWOC) system. In particular, the present study can be helpful to researchers and engineers in modelling the effects of air–sea interface, bubble scattering and particulate scattering on the power budget, channel impulse response and signal-to-noise ratio (SNR) of a vertical communication link between aerial and underwater platforms.
4 citations