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WDM-based bidirectional chaotic communication for semiconductor lasers system with time delay concealment
摘要： In this paper, we propose a wavelength-division-multiplexing (WDM)-based chaos communication configuration allowing for the bidirectional exchange of information. In the scheme, the output of a master semiconductor laser (MSL), is injected into slave semiconductor lasers (SSLs), drives the chaotic synchronization of SSLs with optical feedback and electro-optical phase feedback. By calculating the largest Lyapunov exponent (LLE), Lempel–Ziv complexity (LZC) and permutation entropy (PE), we find that the system can generate the chaotic signal with high complexity. We also demonstrate that the chaotic signal bandwidth obtained is as high as 24.68 GHz by selecting the suitable parameters; this configuration intrinsically conceals the electro-optical phase feedback time delay signature (TDS) and optical feedback TDS in transmitted variable; this delayed chaotic dynamics are identically synchronized when the parameters of emitter are exactly matched with that of receiver; while the external and internal parameters’ mismatch between emitter and receiver can lead to the decrease of the synchronization quality. In addition, the result reveals that the channel spacing has influence on cross-correlation coefficient (XCF) quantifying synchronization quality. At last, the messages introduced at two ends of the link can be successfully encrypted and decrypted, and we quantitatively analyze the corresponding Q-factor at different transmission rates.
关键词： Semiconductor lasers,Optical chaos,Time delay signature concealment,All-optical network,bandwidth
更新于2025-09-23 15:21:01
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A delayed-feedback filter with negative group delay
摘要： A filter with delay-induced negative group delay is presented. The filter consists of multiple time-delayed feedback terms, which lead to a negative group delay for frequencies in the baseband. It can be used for the real-time prediction of band-limited signals. The filter is universal as it does not rely on a specific model of the signal. Specifically, as long as the signal to be predicted is band-limited with a known cutoff frequency, the filter predicts the signal in real time up to a prediction horizon that depends on the cutoff frequency. How signal prediction arises from the negative group delay of the filter is worked out in detail. Its properties, including stability, are derived analytically and demonstrated by numerical simulations. For chaotic systems, the filter is predictive during phases of high predictability.
关键词： real-time prediction,signal prediction,chaotic systems,negative group delay,band-limited signals
更新于2025-09-23 15:21:01
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A Modified Min-Norm for Time Delay and Interface Roughness Estimation by Ground Penetrating Radar: Experimental Results
摘要： The development of methods and tools for the road infrastructure sustainable management is a research challenge, especially for nondestructive testing methods. This letter focuses on the estimation of the thickness of civil engineering structures, like pavements, and more precisely, the time delay and interface roughness. We propose a modified Min-Norm algorithm which allows efficiently estimating the time delay and interface roughness without the eigenvalue decomposition. Therefore, it has a smaller computational load compared with subspace-based methods. The experimental results show the efficiency of the proposed algorithm.
关键词： time delay estimation,interface roughness,pavement survey,Ground penetrating radar (GPR)
更新于2025-09-23 15:21:01
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Pulse Signal Propagation in Bragg-Type Layered Structures
摘要： Propagation of sinc(x), Gaussian, Lorenz, and exponential time pulses in Bragg reflectors, resonators with walls in the form of Bragg reflectors is under consideration. The influence of the number of layers in elements of the structure on the form of pulse is studied. The analysis is done in the comparison with properties of the structure in frequency domain including behavior of zeros of frequency characteristic. Influence of properties of zeros and minimal-phase characteristics on negative group delay manifestation is revealed. The application of exponential approximation of time-domain signals is investigated.
关键词： Bragg-type layered structures,exponential time pulses,zero,Gaussian,Lorenz,negative delay
更新于2025-09-23 15:21:01
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Analysis of Homogeneous Waveguides via the Meshless Radial Basis Function-Generated-Finite-Difference Method
摘要： A time-delay switch (TDS) attack on a control system is caused by adversaries that strategically imbed time delays into such systems. TDS attacks can make a control system, or more specifically a distributed power control system, unstable. Time delays can be introduced in the sensing loop (SL) or control lines. This paper describes a novel, simple, and effective method to thwart TDS attacks on SL. The proposed method works by augmenting the controller with a time-delay estimator to estimate any time delays. The modified controller controls the system under TDS attack. Also, the time-delay estimator will track time delays introduced by an adversary using a modified model reference control with an indirect supervisor and a modified least mean square minimization technique.
关键词： time-delay estimation,model reference control,Time-delay switch attack
更新于2025-09-23 15:19:57
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A comparative study of thermal impact on erbium doped distributed feedback fiber laser output power
摘要： A time-delay switch (TDS) attack on a control system is caused by adversaries that strategically imbed time delays into such systems. TDS attacks can make a control system, or more specifically a distributed power control system, unstable. Time delays can be introduced in the sensing loop (SL) or control lines. This paper describes a novel, simple, and effective method to thwart TDS attacks on SL. The proposed method works by augmenting the controller with a time-delay estimator to estimate any time delays. The modified controller controls the system under TDS attack. Also, the time-delay estimator will track time delays introduced by an adversary using a modified model reference control with an indirect supervisor and a modified least mean square minimization technique.
关键词： time-delay estimation,model reference control,Time-delay switch attack
更新于2025-09-23 15:19:57
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[IEEE 2020 IEEE International Solid- State Circuits Conference - (ISSCC) - San Francisco, CA, USA (2020.2.16-2020.2.20)] 2020 IEEE International Solid- State Circuits Conference - (ISSCC) - 19.2 A 110mK 295?μW 28nm FDSOI CMOS Quantum Integrated Circuit with a 2.8GHz Excitation and nA Current Sensing of an On-Chip Double Quantum Dot
摘要： An electromagnetic wave propagating through the ionosphere is subject to path delay and the depolarizing effect of Faraday rotation, both of which are dependent on global position and geometry. These effects introduce error and consequently reduce the range resolution of remote sensing polarimetric measurements. Satellite-to-ground communications may be adversely altered by these effects so as to inhibit signal reception. The work presented here introduces a simple vectorized model for a large-field-of-view, low-Earth-orbit, satellite system that yields Faraday rotation and path delay according to global position and geometric parameters. Comparison is made with current models, through the simulation of Faraday rotation and path delay. The presented work may extend the range over which Faraday rotation and path delay estimation are reliable. The work presented forms part of a large-field-of-view, low-Earth-orbit satellite model exploiting multiple-input multiple-output polarimetry in three dimensions.
关键词： remote sensing,Faraday rotation,ionosphere,path delay,satellite communications
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Photomedicine and Its Place in Medicine of the 21th Century
摘要： Digital television signal is a promising signal of opportunity for wireless positioning. This paper studies the time of arrival (TOA) estimation on the European standard DVB-T signals in the context of positioning. Theoretical analysis on the autocorrelation of the pilot signal and multipath error envelop suggests that DVB-T has the appropriate characteristics for positioning. A software defined radio-based DVB-T receiver is developed for field testing, in which the radio frequency DVB-T signals are first sampled by universal software radio peripheral, and then algorithms of the coarse symbol synchronization, the pilot detection, the first path acquisition, and the delay tracking are sequentially performed to obtain the TOA estimation. To quantify the TOA tracking results on real DVB-T signals, field testing campaigns are carried out in five cities in Southern France. Test results showed that, in the high signal-noise ratio condition, the 2-σ error interval is within 1 m. By taking into account all the field tests, the interval of 95% accuracy is within 4 m and the corresponding C/N0 varies from 48 to 62 dB-Hz. In addition, with the developed TOA estimation method, the synchronization of the emitters with global positioning system time is evaluated and the distance difference of the multiple emitters within single frequency networks are also measured during the tests.
关键词： delay locked loop,software defined radio (SDR),wireless positioning,Digital TV,orthogonal frequency division multiplexing (OFDM),time of arrival
更新于2025-09-23 15:19:57
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Spectral characteristic of laser-induced plasma in soil
摘要： The spectral characteristic of laser-induced plasma in soil was studied in this work, plasma under the condition of different time delays and irradiances. Moreover, the time evolution characteristics of plasma temperature and electron density were discussed. Within the time delay range of 0–5 μs, the spectral intensity of the characteristic lines of Si Ⅰ: 288.158 nm, Ti Ⅰ: 336.126 nm, Al Ⅰ: 394.400 nm and Fe Ⅰ: 438.354 nm of the four main elements in two kinds of national standard soil decayed exponentially with time. The average lifetime of the spectral lines was nearly 1.56 μs. Under the condition of different time delays, the spectral intensity of Pb Ⅰ: 405.78 nm in soil increased linearly with laser energy. However, the slope between the spectral intensity and laser energy decreased exponentially with the increase of time delay, from 4.91 to 0.99 during 0–5 μs. The plasma temperature was calculated by the Boltzmann plot method and the electron density was obtained by inversion of the full width at half maximum (FWHM) of the spectrum. The plasma temperature decreased from 8900 K to 7800 K and the electron density decreased from 1.5×1017 cm-3 to 7.8×1016 cm-3 in the range of 0–5 μs.
关键词： soil,time delay,electron density,laser energy,LIBS,plasma temperature
更新于2025-09-23 15:19:57
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New Method for Studying the Ignition Characteristics of Condensed Systems by Laser Radiation
摘要： A method for determining the characteristics of laser ignition of the condensed systems is presented, which ensures uniform distribution of the heat flux density over the surface during ignition. The method consists in measuring the ignition delay time of a rotating cylindrical sample when the continuous laser heat flux is applied to its end surface. The theoretical estimation of the required angular rotation velocity of the sample is carried out, which ensures averaging with a given error of the radiation flux density on the surface of the sample, as well as the degree of surface cooling due to the convective heat transfer. The experimental results on the pyroxylin sample ignition at the radiant heating by a CO2 laser with and without rotation of the sample are presented.
关键词： pyroxylin,laser ignition,ignition delay time,condensed system,convective heat transfer,angular velocity of rotation
更新于2025-09-23 15:19:57