... Scintillation of a laser beam propagation through non-Kolmogorov strong turbulence. Peng Deng... more ... Scintillation of a laser beam propagation through non-Kolmogorov strong turbulence. Peng Deng a , Xiuhua Yuan Corresponding Author Contact Information , a , E-mail The Corresponding Author , Dexiu Huang a. a, Wuhan National ...
The nonlinear dependence of the modulation bandwidth and electrical to optical conversion on the ... more The nonlinear dependence of the modulation bandwidth and electrical to optical conversion on the drive current of white LEDs were investigated by comparing novel analytical modeling and experimental measurement for visible light communications.
Novel Optical Systems Design and Optimization XIV, 2011
ABSTRACT The free space optical communication systems should utilize optical antennas with beam t... more ABSTRACT The free space optical communication systems should utilize optical antennas with beam tracking mechanisms. However, the narrow field of view and optical aberration of antennas degrade the tracking performance of the system. In order to overcome the problems, we investigate the wide field of view optical antenna technology. The optical antenna consists of fisheye lens, compensating lens and a catadioptric telescope with off-axis aspheric surface mirrors. The structures and performances of the optical device elements are numerically analyzed so that their designs can make positive contribution in enlarging the field of view and reducing the optical aberration. The final optical antenna design is presented, along with the evaluation of optical performance and tracking characteristics. The proposed optical antenna could not only provide a wide field of view with approximately 60 degree and expand the range for tracking mechanism, but also mitigate the optical aberration and improve tracking accuracy of free space optical communication systems in turbulent atmosphere.
We propose a wide field-of-view optical receiver design based on a fisheye lens and an off-axis c... more We propose a wide field-of-view optical receiver design based on a fisheye lens and an off-axis catadioptric structure for free-space optical communications. The design utilizes a novel fisheye lens group to compress a wide field angle into a narrow field angle and produce the appropriately collimated light that can effectively be coupled into the following aperture of a catadioptric telescope. An off-axis catadioptric telescope with aspheric surface mirrors is designed to compress the incident beam spot size, compensate for the high order optical aberrations and eliminate light loss due to an obstruction. The parallel exit rays are reflected on a double-level tracking mechanism by feeding the position signal from a quadrant detector to correct the pointing error and optimize the coupling efficiency into an optical fiber. The final wide field-of-view optical receiver design is presented along with the evaluation of optical performance results and tracking characteristics. The proposed optical receiver not only can provide a 60-deg wide field-of-view to expand the tracking range, but also mitigates optical aberrations to improve the tracking accuracy for free space optical communication systems in a turbulent atmosphere.
Atmospheric turbulence causes strong irradiance fluctuations of propagating optical wave under th... more Atmospheric turbulence causes strong irradiance fluctuations of propagating optical wave under the severe weather conditions in long-distance free space optical communication. In this paper, the scintillation index for a Gaussian beam wave propagation through non-Kolmogorov turbulent atmosphere is derived in strong fluctuation regime, using non-Kolmogorov spectrum with a generalized power law exponent and the extended Rytov theory with a modified spatial filter function. The analytic expressions are obtained and then used to analyze the effect of power law, refractive-index structure parameter, propagation distance, phase radius of curvature, beam width and wavelength on scintillation index of Gaussian beam under the strong atmospheric turbulence. It shows that, with the increasing of structure parameter or propagation distance, scintillation index increases sharply up to the peak point and then decreases gradually toward unity at rates depending on power law. And there exist optimal value of radius of curvature and beam width for minimizing the value of scintillation index and long wavelength for mitigating the effect of non-Kolmogorov strong turbulence on link performance.
Visible light communications (VLC) based on light-emitting diodes (LEDs) combines lighting and da... more Visible light communications (VLC) based on light-emitting diodes (LEDs) combines lighting and data communications in applications of Internet-of-Things, ad-hoc networks and 5G networks, due to their high energy efficiency, spectral efficiency, security and reliability. We experimentally demonstrate a software-defined real-time multiple input multiple output (MIMO) visible light communication system using Single-Carrier Quadrature Amplitude Modulation (SC-QAM). The system uses two independent phosphorescent white LED transmitters with 10MHz bandwidth in the absence of blue filters, and two independent 150 MHz P-I-N photodiode optical receivers. Real-time MIMO signal processing is implemented by using the Field Programmable Gate Array (FPGA) based Universal Software Radio Peripheral (USRP) devices. Modulation formats and MIMO schemes are software-defined through USRP devices without changing the transceiver hardware. We measured and compared the constellation diagram, error vector magnitude (EVM) and bit error rate (BER) performance for single-carried M-QAM MIMO VLC using spatial diversity and spatial multiplexing. We demonstrate a real-time Single-Carrier 256-QAM 2x2 spatial multiplexing MIMO VLC link and achieve 1.81% averaged EVM, 2x10-5 BER and 12.3 b/s/Hz spectral efficiency over 2 m free space indoor transmission. The experimental results show that spatial diversity MIMO VLC improves error performance at the cost of spectral efficiency that spatial multiplexing should enhance.
We study the average capacity performance for multiple-input multiple-output (MIMO) free-space op... more We study the average capacity performance for multiple-input multiple-output (MIMO) free-space optical (FSO) communication systems using multiple partially coherent beams propagating through non-Kolmogorov strong turbulence, assuming equal gain combining diversity configuration and the sum of multiple gamma-gamma random variables for multiple independent partially coherent beams. The closed-form expressions of scintillation and average capacity are derived and then used to analyze the dependence on the number of independent diversity branches, power law α, refractive-index structure parameter, propagation distance and spatial coherence length of source beams. Obtained results show that, the average capacity increases more significantly with the increase in the rank of MIMO channel matrix compared with the diversity order. The effect of the diversity order on the average capacity is independent of the power law, turbulence strength parameter and spatial coherence length, whereas these effects on average capacity are gradually mitigated as the diversity order increases. The average capacity increases and saturates with the decreasing spatial coherence length, at rates depending on the diversity order, power law and turbulence strength. There exist optimal values of the spatial coherence length and diversity configuration for maximizing the average capacity of MIMO FSO links over a variety of atmospheric turbulence conditions.
... Scintillation of a laser beam propagation through non-Kolmogorov strong turbulence. Peng Deng... more ... Scintillation of a laser beam propagation through non-Kolmogorov strong turbulence. Peng Deng a , Xiuhua Yuan Corresponding Author Contact Information , a , E-mail The Corresponding Author , Dexiu Huang a. a, Wuhan National ...
The nonlinear dependence of the modulation bandwidth and electrical to optical conversion on the ... more The nonlinear dependence of the modulation bandwidth and electrical to optical conversion on the drive current of white LEDs were investigated by comparing novel analytical modeling and experimental measurement for visible light communications.
Novel Optical Systems Design and Optimization XIV, 2011
ABSTRACT The free space optical communication systems should utilize optical antennas with beam t... more ABSTRACT The free space optical communication systems should utilize optical antennas with beam tracking mechanisms. However, the narrow field of view and optical aberration of antennas degrade the tracking performance of the system. In order to overcome the problems, we investigate the wide field of view optical antenna technology. The optical antenna consists of fisheye lens, compensating lens and a catadioptric telescope with off-axis aspheric surface mirrors. The structures and performances of the optical device elements are numerically analyzed so that their designs can make positive contribution in enlarging the field of view and reducing the optical aberration. The final optical antenna design is presented, along with the evaluation of optical performance and tracking characteristics. The proposed optical antenna could not only provide a wide field of view with approximately 60 degree and expand the range for tracking mechanism, but also mitigate the optical aberration and improve tracking accuracy of free space optical communication systems in turbulent atmosphere.
We propose a wide field-of-view optical receiver design based on a fisheye lens and an off-axis c... more We propose a wide field-of-view optical receiver design based on a fisheye lens and an off-axis catadioptric structure for free-space optical communications. The design utilizes a novel fisheye lens group to compress a wide field angle into a narrow field angle and produce the appropriately collimated light that can effectively be coupled into the following aperture of a catadioptric telescope. An off-axis catadioptric telescope with aspheric surface mirrors is designed to compress the incident beam spot size, compensate for the high order optical aberrations and eliminate light loss due to an obstruction. The parallel exit rays are reflected on a double-level tracking mechanism by feeding the position signal from a quadrant detector to correct the pointing error and optimize the coupling efficiency into an optical fiber. The final wide field-of-view optical receiver design is presented along with the evaluation of optical performance results and tracking characteristics. The proposed optical receiver not only can provide a 60-deg wide field-of-view to expand the tracking range, but also mitigates optical aberrations to improve the tracking accuracy for free space optical communication systems in a turbulent atmosphere.
Atmospheric turbulence causes strong irradiance fluctuations of propagating optical wave under th... more Atmospheric turbulence causes strong irradiance fluctuations of propagating optical wave under the severe weather conditions in long-distance free space optical communication. In this paper, the scintillation index for a Gaussian beam wave propagation through non-Kolmogorov turbulent atmosphere is derived in strong fluctuation regime, using non-Kolmogorov spectrum with a generalized power law exponent and the extended Rytov theory with a modified spatial filter function. The analytic expressions are obtained and then used to analyze the effect of power law, refractive-index structure parameter, propagation distance, phase radius of curvature, beam width and wavelength on scintillation index of Gaussian beam under the strong atmospheric turbulence. It shows that, with the increasing of structure parameter or propagation distance, scintillation index increases sharply up to the peak point and then decreases gradually toward unity at rates depending on power law. And there exist optimal value of radius of curvature and beam width for minimizing the value of scintillation index and long wavelength for mitigating the effect of non-Kolmogorov strong turbulence on link performance.
Visible light communications (VLC) based on light-emitting diodes (LEDs) combines lighting and da... more Visible light communications (VLC) based on light-emitting diodes (LEDs) combines lighting and data communications in applications of Internet-of-Things, ad-hoc networks and 5G networks, due to their high energy efficiency, spectral efficiency, security and reliability. We experimentally demonstrate a software-defined real-time multiple input multiple output (MIMO) visible light communication system using Single-Carrier Quadrature Amplitude Modulation (SC-QAM). The system uses two independent phosphorescent white LED transmitters with 10MHz bandwidth in the absence of blue filters, and two independent 150 MHz P-I-N photodiode optical receivers. Real-time MIMO signal processing is implemented by using the Field Programmable Gate Array (FPGA) based Universal Software Radio Peripheral (USRP) devices. Modulation formats and MIMO schemes are software-defined through USRP devices without changing the transceiver hardware. We measured and compared the constellation diagram, error vector magnitude (EVM) and bit error rate (BER) performance for single-carried M-QAM MIMO VLC using spatial diversity and spatial multiplexing. We demonstrate a real-time Single-Carrier 256-QAM 2x2 spatial multiplexing MIMO VLC link and achieve 1.81% averaged EVM, 2x10-5 BER and 12.3 b/s/Hz spectral efficiency over 2 m free space indoor transmission. The experimental results show that spatial diversity MIMO VLC improves error performance at the cost of spectral efficiency that spatial multiplexing should enhance.
We study the average capacity performance for multiple-input multiple-output (MIMO) free-space op... more We study the average capacity performance for multiple-input multiple-output (MIMO) free-space optical (FSO) communication systems using multiple partially coherent beams propagating through non-Kolmogorov strong turbulence, assuming equal gain combining diversity configuration and the sum of multiple gamma-gamma random variables for multiple independent partially coherent beams. The closed-form expressions of scintillation and average capacity are derived and then used to analyze the dependence on the number of independent diversity branches, power law α, refractive-index structure parameter, propagation distance and spatial coherence length of source beams. Obtained results show that, the average capacity increases more significantly with the increase in the rank of MIMO channel matrix compared with the diversity order. The effect of the diversity order on the average capacity is independent of the power law, turbulence strength parameter and spatial coherence length, whereas these effects on average capacity are gradually mitigated as the diversity order increases. The average capacity increases and saturates with the decreasing spatial coherence length, at rates depending on the diversity order, power law and turbulence strength. There exist optimal values of the spatial coherence length and diversity configuration for maximizing the average capacity of MIMO FSO links over a variety of atmospheric turbulence conditions.
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