- 标题
- 摘要
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Experimental study of the effects of thermally induced optical turbulence on underwater wireless optical communication link parameters
摘要： In this experimental research, the effects of refractive index fluctuations resulting from temperature fluctuations on some of the most important underwater communication link parameters such as the average received power, Signal to Noise Ratio (SNR) and normalized power variance (aperture averaged scintillation) has been experimentally investigated. Moreover, by introducing a new probability density function which is fitted more appropriately to the experimental data obtained from our simulator tank, the Bit Error Rate (BER) behavior of an Underwater Wireless Optical Communication (UWOC) link is also studied. These investigations are essential due to the optical turbulence limiting effects on the performance of UWOC systems. The experimental results indicate that reduction of the aperture averaged scintillation effects by using of optical components in the transmitter and receiver of UWOC links can enhance their performance. In general, increasing the strength of the optical turbulence (by increasing the temperature gradient induced by the rod heater) or the distance of the localized turbulence screen generated by temperature gradient from the transmitter plane, the aperture averaged scintillation decreases and consequently the SNR raises whilst the BER declines. Also, expanding the aperture diameter of the receiver optics reduces the normalized power variance which leads to decrease and increase in the BER and the SNR amounts respectively. The results are presented as experimental simulation graphs.
关键词： Laser beam propagation through turbulence,aperture averaged scintillation,Probability density function,BER,SNR,Underwater optical communication link
更新于2025-09-12 10:27:22
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Free Space Optical Communication (System Design, Modeling, Characterization and Dealing with Turbulence) || 2. Real-time measurement of meteorological parameters for estimating low altitude atmospheric turbulence strength (C2 n)
摘要： The major factor that limits the performance of Free Space Optical Communication (FSOC) is atmospheric turbulence which fluctuates over time in accordance with the variations in local meteorological parameters. Estimating the atmospheric turbulence strength (C2n) from measurement data is significant for finding the data rate the system is capable of operating at under different outdoor local environmental conditions. Hence, a low cost customized system for continuously measuring local meteorological data is developed and presented in this chapter. A field test scintillometer setup is established for a link range of 0.5 km at an altitude of 15.25 m. Specialized sensors are interfaced to the digital architectures to acquire the real-time data corresponding to atmospheric changes. The accuracy and performance of the measurement system are tested against standard instruments and the maximum correlation coefficients of 99.92 %, 99.63 %, 99.73 %, and 99.88 % are achieved for wind speed, temperature, relative humidity and pressure respectively. Atmospheric turbulence strength is estimated for the diurnal period using measured meteorological data. The validations of the estimated results with the scintillometer measurement are also analyzed. The weather profile and corresponding C2n variations at our test field for different seasons over a one year period are presented and the results are analyzed.
关键词： atmospheric turbulence,meteorological parameters,scintillometer,PAMELA model,Free Space Optical Communication (FSOC)
更新于2025-09-12 10:27:22
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Free Space Optical Communication (System Design, Modeling, Characterization and Dealing with Turbulence) || 6. Quality metrics and reliability analysis of ground-to-ground free space laser communication in different weather conditions together with beam steering system
摘要： Over the past two decades Free Space Optical Communication (FSOC) has become more and more interesting as an adjunct or alternative to Radio Frequency (RF) communication. Optical wave propagation in an FSOC channel is severely affected by turbulent atmospheric parameters and they lead to the degradation of the data transmission quality and reliability. Among the various atmospheric effects, beam wandering is the main cause for major power loss and cannot be solved without incorporation of a Beam Wandering Compensation (BWC) control system. Therefore, a closed form treatment describing beam wandering effect mitigation is required. Simplex FSOC data transmission (data rate is 155 Mbps) transmitter-receiver experimental setups are established for the data link range of 0.5 km at an altitude of 15.25 m at the college campus. A near IR 850 nm optical source is used for data transmission. The more accurate values of atmospheric attenuation (Atten) and turbulence strength (C2n) are obtained using the new models developed according to local weather data. The transmittance of the FSOC channel is calculated using the estimated atmospheric attenuation. The methods of measuring the Q-factor and Bit Error Rate (BER) by postprocessing the received signal are described and used to validate the performance of the FSOC system. The improvements on received signal strength and centroid stability by incorporating the BWC control system are analyzed with various communication key parameters in the very weak to very strong atmospheric turbulence conditions. The average BER at a value of 9.82 ? 10?9 is maintained with the Q-factor value of ≈ 6 in almost all atmospheric turbulence conditions with compensating beam wandering effects, i.e. pointing error losses. Evidence of the suitability and effectiveness of the developed controller in terms of received power (Pr), transmittance (T), eye diagram, Q-factor, Signal to Noise Ratio (SNR), BER, link margin and decoding decision threshold values are comprehensively analyzed through experimental results and reported in this chapter.
关键词： atmospheric turbulence,Beam Wandering Compensation (BWC),Q-factor,Signal to Noise Ratio (SNR),Bit Error Rate (BER),Free Space Optical Communication (FSOC)
更新于2025-09-12 10:27:22
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Tapping underwater wireless optical communication in pure water and natural Dead-Sea ultra-high-salinity water by diffraction grating
摘要： Although underwater wireless optical communication (UWOC) receives much interest lately, security issues associated with it get little attention. In this paper, we show how a message communicated using UWOC can be eavesdropped without a sender's or addressee's awareness, by employing a diffraction grating. We also analyze the propagation of multiple diffracted Gaussian beams in water, and show for the first time that UWOC is feasible even in natural ultra-salty water taken from the Dead-Sea. We evaluate how far from the addressee the message could be eavesdropped, and discuss different possibilities of tapping the channel – one from the air and one underwater.
关键词： diffraction grating,eavesdropping,underwater wireless optical communication,ultra-salty water,UWOC,Dead-Sea
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Green and Human Information Technology (ICGHIT) - Kuala Lumpur, Malaysia (2019.1.15-2019.1.17)] 2019 International Conference on Green and Human Information Technology (ICGHIT) - Development of Python-MATLAB Interface Program for Optical Communication System Simulation
摘要： This paper reports on the results of a developing Python-MATLAB interface program to implement optical wireless communication system simulation. We implement Python interface for entering input values and simulation environment variables for MATLAB. We operate MATLAB to numerical computing process about communication system simulation to generate a signal, to approximate channel characteristics and to recover the signal. Python passes input data and environment variables to MATLAB and displays output data and graphs from the simulation after MATLAB numerical computing.
关键词： Simulation,MATLAB,optical communication,Python
更新于2025-09-12 10:27:22
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[IEEE 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Xi'an, China (2019.6.19-2019.6.21)] 2019 14th IEEE Conference on Industrial Electronics and Applications (ICIEA) - Signature-Based Morse Code Encoding for a LED-Based optical Layer 2 data communication
摘要： With the rapid improvements in engineering technology, underwater communications have gained major interests from researchers with application areas from commercial to military water based communication systems. However, underwater wireless communication is challenging and difficult compared to wireless terrestrial as it can be easily interrupted due to interference from harsh underwater operation conditions, noise, limited bandwidth and power resources. Various researches in underwater acoustic, optical, and RF communications for secured and reliable underwater wireless network have been carried out. In this paper, an LED based optical wireless communications is proposed using a layered 2 Morse-code based encoding protocol for short distance underwater communication. The proposed system converts the data into a serial of dots and spaces before it is transmitted using the LED as a light source. At the receiver end, the system decodes sequences of on-off light sensed by the photo-diode into the data. The main contribution of this work is the design of a layer 2 signature-based encoding and decoding systems for short range wireless underwater optical communication protocol that can provide a higher data rates compared to traditional acoustic systems with significant lower power consumption and simpler computational complexity. The transmission protocol is evaluated in a dark room and in a water medium. The results have shown above 90% transmission success rate. The result also showed that different colors of the LED emission can affect the reliability of data transmission.
关键词： LED,Transmission Protocol,Optical Communication,Morse Code,Underwater Communication
更新于2025-09-11 14:15:04
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[IEEE 2019 International Conference on Opto-Electronics and Applied Optics (Optronix) - Kolkata, India (2019.3.18-2019.3.20)] 2019 International Conference on Opto-Electronics and Applied Optics (Optronix) - Design of High-Performance LED Based Integrating Sphere for Illumination & Communication
摘要： An integrating sphere has been specially designed using multiple white light LEDs mounted on both the inner and outer surfaces of the sphere to create improved uniform illumination inside a computer laboratory room. The LEDs are simultaneously used as optical transmitters of trans-receiver systems for indoor optical wireless communication. More uniformity of light helps to develop better access to wireless communication systems, comfortable movement inside the room and reduced shadowing effect in wireless communication. One integrating sphere fitted with LED arrays divided among outer and the inner surfaces of the sphere is able to create ideal uniformity conditions for illumination and data communication within a volume (3 x 3 x 3) m3 of laboratory space. The system is capable of bidirectional full-duplex communication using IR LEDs as source for uplink and silicon photodiodes as receivers for optical wireless communication links. The theory and the design principles of the integrating sphere and the optical wireless communication link design would be presented.
关键词： integrating sphere,optical communication,wireless communication,uniform illumination,white light LED
更新于2025-09-11 14:15:04
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Micro‐ and Nanolasers
摘要： A laser is a device that emits strong coherent light through a process of light amplification by stimulated emission of radiation. The theoretical foundation for the laser was established by Albert Einstein theorizing on the existence of stimulated emission in 1916. The first laser was built by Theodore Maiman in 1960 based on the theoretical work of Charles Townes and Arthur Schawlow. The invention and continuous development of the laser has revolutionized science, technology, and industry. Miniaturization of lasers has been promoting the development and application of laser technology. For example, compact semiconductor lasers have become an integral part of our everyday life. With the development of micro- and nanofabrication technology, including both top-down and bottom-up techniques, the dimensions of lasers have been shrunk down to micro- and nanoscale. With an unprecedented ability to deliver intense coherent light at (sub)wavelength scale, such micro- and nanolasers are promising to trigger the next revolution in the laser and related fields. Indeed, the micro- and nanolasers are or will be unlocking their potential in photonic and optoelectronic applications, such as chemical and biological sensing, laser display and holography, on-chip optical communication and processing, and so on.
关键词： micro- and nanolasers,on-chip optical communication and processing,chemical and biological sensing,photonic and optoelectronic applications,laser display and holography
更新于2025-09-11 14:15:04
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Blind Carrier Frequency Offset Estimation in Coherent Optical Communication Systems with Probabilistically Shaped M-QAM
摘要： We find that the conventional 4th power and circular harmonic expansion (CHE) algorithms, which are originally devised for blind frequency offset estimation (FOE) in the uniform M-quadrature amplitude modulation (MQAM) systems, cannot work properly for probabilistically shaped (PS)-MQAM under moderate or strong shaping. To solve this issue, two novel blind FOE algorithms, namely the radius directed (RD)-4th power algorithm and the generalized circular harmonic expansion (GCHE) algorithm, are proposed. The former one adopts QPSK-selection based on a radius threshold optimized for a specific constellation entropy; while the later one conducts maximum likelihood (ML) estimation with a theoretically derived nonlinear radius transfer function in the GCHE.
关键词： Carrier frequency offset estimation,coherent optical communication,probabilistically shaped (PS) M-quadrature amplitude modulation (MQAM)
更新于2025-09-11 14:15:04
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Performance analysis of 349-element adaptive optics unit for a coherent free space optical communication system
摘要： As a continuation of our previous work [Optics Express.25, 15229(2017)] in which we have verified the performance of a coherent free space optical communication (FSOC) system with a 97-element adaptive optics (AO) system, in this paper, we evaluated the performance improvement of the coherent FSOC system using a large-scale high-speed AO system with a 349-element continuous surface deformable mirror. The mixing efficiency (ME) and bit-error-rate (BER) under different Greenwood frequency (GF) were calculated as the performance metric of coherent FSOC system. The performance of FSOC system using such a large-scale AO system was quantitatively verified for the first time. The obtained results showed that the performance was obviously improved when a larger-scale high-speed AO system is employed in coherent FSOC system. This analysis result provides a performance verification for large-scale high-speed AO systems used in FSOC system which is beneficial for coherent FSOC system parameters design.
关键词： bit-error-rate,adaptive optics,free space optical communication,coherent detection,mixing efficiency
更新于2025-09-11 14:15:04