In this paper, a radio frequency-underwater wireless optical communication (RF-UWOC) dual-hop decode-and forward (DF) relaying link for Satellite-Underwater communication is proposed to extend the communication distance based on RF and underwater optical wireless communication technology. The communication system consists of satellite, surface relay platform and underwater destination node, where the RF communication technology is adopted for satellite surface relay link, which is modeled as Rician fading distributions considering rain and snow attenuation. Surface relay platform and underwater destination node adopt underwater wireless optical communication (UWOC, and the link is modeled as Gamma-Gamma fading distributions considering sea water absorption and scattering. The closed-form mathematical expression of the RF link channel models and the UWOC link channel models is derived and analyzed, the outage probability (OP) and average bit error rate (ABER) performance of the satellite-underwater (RF-UWOC) dual-hop decode-and-forward (DF) relaying communication link is investigated and simulated.
This paper designs and analysis a high speed underwater radio over free space optical (RoFSO) communication link for underwater wireless optical communication application, which mainly consist of 1064nm light source, modulator, periodically poled lithium niobate (PPLN) frequency doubling crystal, optical transceiver antenna and detector. The PPLN frequency doubling crystal is applied to generate 532nm light wave signals with high speed modulation format based on second harmonic generation theory, when a high speed modulated 1064 nm continuous-wave laser signal is inputted. The communication performance of transmitting BPSK modulation format signal of the underwater RoFSO is investigated in Gamma-Gamma ocean turbulence fading channel distribution. The expression of bit error rate (BER) and average outage probability are derived and the results of both theoretical analysis and numerical simulations are obtained by Matlab software in ocean turbulence. The results of numerical simulations show that the communication performance of underwater RoFSO is better than the common OOK direct modulation UWOC system.
KEYWORDS: Free space optics, Turbulence, Signal to noise ratio, Wireless communications, Signal attenuation, Modulation, Mathematical modeling, Data communications, Submerged target modeling, Receivers
This paper presents a hybrid FSO-UWOC dual-hop link for air-ocean high speed wireless optical communication application, where the Gamma-Gamma fading channel distribution is adopted to model the atmospheric turbulence and ocean turbulence. Assuming decode-and-forward (DF) relay scheme and BPSK modulation technology, the mathematical expressions of bit error rate (BER) and outage probability are derived and analyzed for the dual-hop link over turbulence channel. Numerical simulations are presented to verify the accuracy of the mathematical analytical expressions of the hybrid FSO-UWOC dual-hop link.
Most existing image-sensor-based indoor visible light positioning (VLP) systems use multiple light-emitting diodes (LEDs) or dual image sensor for vision analysis and have the disadvantage of the high computational cost of image processing. Moreover, most VLP systems are not practical for real-life use due to fixed image sensor orientation and lake of consideration on the tilt angle of the image sensor, and the effective positioning area is limited. In this paper, we propose a space-efficient and reality-efficient VLP method based on tilt single image sensor using single LED, which increases the effective positioning area, the reality and flexibility of lighting infrastructure design for real-life use. Based on the proposed method, a high speed and high precision VLP algorithm with commodity mobile phone was proposed, the simulation results show that the maximum positioning error is 5.5 cm and the average positioning error is 2.48 cm, which achieved a centimeter-level positioning accuracy with high positioning speed and large effective positioning area.
This paper presents an silicon-based integrated hybrid detector that can perform the tasks of ultraviolet (UV) light detecting, visible (VIS) light detecting and near-infrared (NIR) light detecting. The detector is based on hybrid photodiodes that uses a vertical p+/N-well/Deep p-well/n-sub junction photodiodes which are available in CMOS processes, and can be configured to work as UV light detector, VIS light detector or NIR light detector in variable light environment by the using of transimpedance amplifier(TIA), subtractor(SUB), comparator and some simple switch logic gates. Device theory, structures, doping profiles and simulations are presented to verify the concept and feasibility. The simulation results show that the three photodiodes present different spectral responses, and dark current is as low as 10-14A, and the optical signal of different wavelength can be effective detected with a high sensitivity and selectivity.
Theory and experimental results show that the state of the circular polarization of laser changes little in the atmospheric channel, and circular polarization modulation technology can improve the performance of free-space optical communication systems. This article starts from the principle of circular polarization modulation technology, introduces several common circular polarization transmission system structure, and then briefly describe its application and research direction in the future.
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