The past decades have witnessed the development of new X-ray beam sources with brightness growing at a rate surpassing Moore’s law.Current and upcoming diffraction limited and fully coherent X-ray beam sources,includ...The past decades have witnessed the development of new X-ray beam sources with brightness growing at a rate surpassing Moore’s law.Current and upcoming diffraction limited and fully coherent X-ray beam sources,including multi-bend achromat based synchrotron sources and high repetition rate X-ray free electron lasers,puts increasingly stringent requirements on stability and accuracy of X-ray optics systems.Parasitic motion errors at sub-micro radian scale in beam transport and beam conditioning optics can lead to significant loss of coherence and brightness delivered from source to experiment.To address this challenge,we incorporated optical metrology based on interferometric length and angle sensing and real-time correction as part of the X-ray optics motion control system.A prototype X-ray optics system was constructed following the optical layout of a tunable X-ray cavity.On-line interferometric metrology enabled dynamical feedback to a motion control system to track and compensate for motion errors.The system achieved sub-microradian scale performance,as multiple optical elements are synchronously and continuously adjusted.This first proof of principle measurement demonstrated both the potential and necessity of incorporating optical metrology as part of the motion control architecture for large scale X-ray optical systems such as monochromators,delay lines,and in particular,X-ray cavity systems to enable the next generation cavity-based X-ray free electron lasers.展开更多
In the past few decades,ion engines have been widely used in deep-space propulsion and satellite station-keeping.The aim of extending the thruster lifetime is still one of the most important parts during the design st...In the past few decades,ion engines have been widely used in deep-space propulsion and satellite station-keeping.The aim of extending the thruster lifetime is still one of the most important parts during the design stage of ion engine.As one of the core components of ion engine,the grid assembly of ion optic systems may experience long-term ion sputtering in extreme electro-thermal environments,which will eventually lead to its structural and electron-backstreaming failures.In this paper,the current studies of the grid assembly erosion process are systematically analyzed from the aspects of sputtering damage process of grid materials,numerical simulations,and measurements of erosion characteristics of grid assembly.The advantages and disadvantages of various erosion prediction models are highlighted,and the key factors and processes affecting the prediction accuracy of grid assembly erosion patterns are analyzed.Three different types of experimental methods of grid assembly erosion patterns are compared.The analysis in this paper is of great importance for selecting the sputter-resistant grid materials,as well as establishing the erosion models and measurement methods to accurately determine the erosion rate and failure modes of grid assembly.Consequently,the working conditions and structure parameters of ion optic systems could be optimized based on erosion models to promote the ion engine lifetime.展开更多
We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigoro...We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigorous noise model of the receiver has been developed for this purpose.We calculate the total noise and sensitivity of the receiver.The front-end of the receiver exhibits a sensitivity of -45 dBm at a bit rate of 1 Gb/s and -30 dBm at a bit rate of 10 Gb/s,and the total mean-square noise curren t〈i2n〉=5×10-15 A2 at a bit rate of 1 Gb/s an d〈i2n〉 =10-12 A2 at a bit rate of 10 Gb/s,and a 3-dB bandwidth of 10 GHz.展开更多
The improved three novel schemes of the super forward error correction （super-FEC） concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existin...The improved three novel schemes of the super forward error correction （super-FEC） concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon（RS）＋ Bose-Chaudhuri-Hocguenghem（BCH） inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS（255,239） ＋RS（255,239） code and the RS（255,239） ＋RS（255,223） code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS（255,239） code and other codes, and their signal to noise ratio gains are respectively 2-3 dB more than that of the RS（255,239）code at the bit error rate of 1 × 10^-13. Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.展开更多
A new concatenated code of RS（255,239）＋BCH（2 040,1 930） code to he suitable for WDM optical transmission systems is proposed. The simulation resuhs show that this new concatenated code. compared with the RS（255,...A new concatenated code of RS（255,239）＋BCH（2 040,1 930） code to he suitable for WDM optical transmission systems is proposed. The simulation resuhs show that this new concatenated code. compared with the RS（255,239）4-CSOC（k0/n0=6/7, J= 8） code in ITU-TG. 75.1, has a lower redundancy and better error-correction performance, furthermore, its net coding gain（NCG） is respectively 0. 46 dB, 0.43 dB morethanthatofRS（255,239）＋CSOC（k0/n0= 6/7, J= 8） code and BCH（3860,3824）＋BCH （2 040,1 930） code in ITU TG. 75. 1 at the third iteration for the bit error rate（BER） of 10^-12. Therefore, the new super forward error correction（Super-FEC） concatenated code can be better used in ultra long-haul, ultra large-capacity and ultra high-speed WDM optical communication systems.展开更多
Equalization can compensate channel distortion caused by channel multipath effects, and effectively improve convergent of modulation constellation diagram in optical wireless system. In this paper, the subspace blind ...Equalization can compensate channel distortion caused by channel multipath effects, and effectively improve convergent of modulation constellation diagram in optical wireless system. In this paper, the subspace blind equalization algorithm is used to preprocess M-ary phase shift keying(MPSK) subcarrier modulation signal in receiver. Mountain clustering is adopted to get the clustering centers of MPSK modulation constellation diagram, and the modulation order is automatically identified through the k-nearest neighbor(KNN) classifier. The experiment has been done under four different weather conditions. Experimental results show that the convergent of constellation diagram is improved effectively after using the subspace blind equalization algorithm, which means that the accuracy of modulation recognition is increased. The correct recognition rate of 16 PSK can be up to 85% in any kind of weather condition which is mentioned in paper. Meanwhile, the correct recognition rate is the highest in cloudy and the lowest in heavy rain condition.展开更多
This paper investigates the performance of multi-hop Free Space Optical(FSO) communications using serial Decode-and-Forward(DF) relay transmissions.A statistical model for the optical intensity fluctuation at the rece...This paper investigates the performance of multi-hop Free Space Optical(FSO) communications using serial Decode-and-Forward(DF) relay transmissions.A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence-induced fading,mis alignment fading and pass-loss is presented.Under given weather and mis alignment conditions,a closed-form analytical expression for the end-to-end outage probability of serial Decode-and-Forward(DF) multi-hop FSO communications is derived.Numerical results show that the serial DF multi-hop transmission is a promising technology to enhance the performance of FSO communications.Moreover,the derived analytical expression can provide close approximations to the simulation results.展开更多
In this work, the performance of free-space optical(FSO) communication system based on maximal ratio combining using binary phase shift keying subcarrier intensity modulation over Gamma-Gamma fading channels has been ...In this work, the performance of free-space optical(FSO) communication system based on maximal ratio combining using binary phase shift keying subcarrier intensity modulation over Gamma-Gamma fading channels has been studied systematically. Under identically or non-identically distributed branches, the analytical expressions for the bit error rate function of signal-to-noise are derived by expressing the modified Bessel function of second kind with Meijer G-function for dualand triple-branch systems, respectively. In terms of H-fox function, the new expressions have more general forms and are more efficient for computation. It is found that the dual-and triple-branch systems significantly outperform the direct link system under weak, moderate and strong turbulence conditions. Monte Carlo simulation is also provided to confirm the accuracy of the proposed model.展开更多
The contradiction between classical and quantum physics can be identified through quantum contextuality, which does not need composite systems or spacelike separation. Contextuality is proven either by a logical contr...The contradiction between classical and quantum physics can be identified through quantum contextuality, which does not need composite systems or spacelike separation. Contextuality is proven either by a logical contradiction between the noncontextuality hidden variable predictions and those of quantum mechanics or by the violation of noncontextual inequality. We propose an experimental scheme of state-independent contextual inequality derived from the Mermin proof of the Kochen–Specker(KS) theorem in eight-dimensional Hilbert space, which could be observed either in an individual system or in a composite system. We also show how to resolve the compatibility problems. Our scheme can be implemented in optical systems with current experiment techniques.展开更多
Driven by advancements in artificial intelligence,end-to-end learning has become a key method for system optimization in various fields,including communications.However,applying learning algorithms such as backpropaga...Driven by advancements in artificial intelligence,end-to-end learning has become a key method for system optimization in various fields,including communications.However,applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature.Existing methods typically require developing a precise differentiable digital model of the physical system,which is computationally complex and can cause significant performance loss after deployment.In response,we propose a novel end-to-end learning framework called physics-guided learning.展开更多
The optical noninvasive diagnostic of characteristic of silicon semiconductor devices by using a InGaAsP/InP semiconductor laser as an optical probe is reported. The principle of experimental method is based on the de...The optical noninvasive diagnostic of characteristic of silicon semiconductor devices by using a InGaAsP/InP semiconductor laser as an optical probe is reported. The principle of experimental method is based on the dependence of the optical refractive index on the carrier charge density in the active region of devices and detection of variation of refractive index by two laser beam interferometric techniques.展开更多
The principle of new optical fibre pressure transducer is analysed, and ingenious design scheme of this transducer is given. This new transducer specimen is provided with following characteristics: experimental transm...The principle of new optical fibre pressure transducer is analysed, and ingenious design scheme of this transducer is given. This new transducer specimen is provided with following characteristics: experimental transmitting distance is 20 m (actually up to 1 000 m ); system sensitivity is 0. 1 mV/Pa; power consumption of the probe is less than 125 μW. Finally, some points of the appraisement are given in this paper.展开更多
The formalism of generalized diffraction integral for paraxial misaligned optical systems is used to investigate the propagation of the Modified Bessel-Gaussian (MBG) beam through a misaligned thin lens. The propertie...The formalism of generalized diffraction integral for paraxial misaligned optical systems is used to investigate the propagation of the Modified Bessel-Gaussian (MBG) beam through a misaligned thin lens. The properties of the propagation of MBG beam traveling through this misaligned ABCD optical system are discussed. A special case of misaligned circular thin lens is illustrated analytically and numerically. The shape of the MBG beam at the exit of the misaligned optical system is unchanged;however the center of the beam is shifted from the propagation axis in correlated manner with the design parameters of the optical system.展开更多
A stable and accurate pointing,acquisition system is an important part of initially building intersatellite optical communication links.Satellite platform vibration can cause the system instability and reduce the syst...A stable and accurate pointing,acquisition system is an important part of initially building intersatellite optical communication links.Satellite platform vibration can cause the system instability and reduce the system precision in building and maintenance of a satellite optical communication system.In this paper,vibration influence is consciously discussed by acquisition time for intersatellite optical communications.Analytical expression of acquisition possibility is derived,taking the scan parameters and platform vibration into account,and vibration influence on the multi-scan acquisition time is also presented.The theoretical result calculated by the proposed analytical expression is approximate to the result by the Monte Carlo simulation.展开更多
Optical Wireless Communication(OWC)is a new trend in communication systems to achieve large bandwidth,high bit rate,high security,fast deployment,and low cost.The basic idea of the OWC is to transmit data on unguided ...Optical Wireless Communication(OWC)is a new trend in communication systems to achieve large bandwidth,high bit rate,high security,fast deployment,and low cost.The basic idea of the OWC is to transmit data on unguided media with light.This system requires multi-carrier modulation such as Orthogonal Frequency Division Multiplexing(OFDM).This paper studies optical OFDM performance based on Intensity Modulation with Direct Detection(IM/DD)system.This system requires a non-negativity constraint.The paper presents a framework for wireless optical OFDM system that comprises(IM/DD)with different forms,Direct Current biased Optical OFDM(DCO-OFDM),Asymmetrically Clipped Optical OFDM(ACO-OFDM),Asymmetrically DC-biased Optical OFDM(ADO-OFDM),and Flip-OFDM.It also considers channel coding as a tool for error control,channel equalization for reducing deterioration due to channel effects,and investigation of the turbulence effects.The evaluation results of the proposed framework reveal enhancement of performance.The performance of the IM/DD-OFDM system is investigated over different channel models such as AWGN,log-normal turbulence channel model,and ceiling bounce channel model.The simulation results show that the BER performance of the IM/DD-OFDM communication system is enhanced while the fading strength is decreased.The results reveal also that Hamming codes,BCH codes,and convolutional codes achieve better BER performance.Also,two algorithms of channel estimation and equalization are considered and compared.These algorithms include the Least Squares(LS)and the Minimum Mean Square Error(MMSE).The simulation results show that the MMSE algorithm gives better BER performance than the LS algorithm.展开更多
A novel scheme of differential polarization demodulation is presented and demonstrated based on a polarized asym- metrical Mach-Zehnder interferometer configuration with polarization control. To enhance the stability ...A novel scheme of differential polarization demodulation is presented and demonstrated based on a polarized asym- metrical Mach-Zehnder interferometer configuration with polarization control. To enhance the stability of the demodulator, a phase-lock device is designed, and it is composed of a symmetric 3 × 3 coupler and a feedback circuit. For further estab- lishing a differential polarization-shift keying （DPolSK） transmission system, we successfully carry out the demodulation experiments on 10-Gb/s DPolSK optical signals for the first time. Due to the all-optical structure with phase-lock, our scheme is available to realize the DPolSK optical communication in practical optical fiber systems.展开更多
Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerabl...Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerably high precision, but it is hard to operate from the viewpoint of operation. The method using contacting lithography technology or laser ablation can be easily operated with the cost of reducing fabrication precision and the trouble of choosing appropriate materials. For all of these methods, the coding of half tone masks with corrections for the nonlinear characteristics of coding, imaging and photoresist is recommended.展开更多
Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd：YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 ...Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd：YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 nm. The reorientation rate of azo polymer films is enhanced in the presence of Ag nanoparticles, and the rate of the azo polymer film with Ag concentration of 2.2 μg/ml is larger than that of the azo polymer films with Ag concentrations of 1.1 μg/ml and 4.4 μg/ml. The third-order nonlinear optical properties of the Ag/azo composite film are obtained by the Z-scan technique at a wavelength of 532 nm, and the measured nonlinear refractive index is 9.258×10-9 esu. It is shown that the main mechanisms involved in the large nonlinear optical responses come from the local field enhancement of Ag nanoparticles and the nonlinear effect of the azo polymer matrix.展开更多
Frequency generation in highly multimode nonlinear optical systems is inherently a complex process,giving rise to an exceedingly convoluted landscape of evolution dynamics.While predicting and controlling the global c...Frequency generation in highly multimode nonlinear optical systems is inherently a complex process,giving rise to an exceedingly convoluted landscape of evolution dynamics.While predicting and controlling the global conversion efficiencies in such nonlinear environments has long been considered impossible,here,we formally address this challenge even in scenarios involving a very large number of spatial modes.By utilizing fundamental notions from optical statistical mechanics,we develop a universal theoretical framework that effectively treats all frequency components as chemical reactants/products,capable of undergoing optical thermodynamic reactions facilitated by a variety of multi-wave mixing effects.These photon-photon reactions are governed by conservation laws that directly determine the optical temperatures and chemical potentials of the ensued chemical equilibria for each frequency species.In this context,we develop a comprehensive stoichiometric model and formally derive an expression that relates the chemical potentials to the optical stoichiometric coefficients,in a manner akin to atomic/molecular chemical reactions.This advancement unlocks new predictive capabilities that can facilitate the optimization of frequency generation in highly multimode photonic arrangements,surpassing the limitations of conventional schemes that rely exclusively on nonlinear optical dynamics.Notably,we identify a universal regime of Rayleigh-Jeans thermalization where an optical reaction at near-zero optical temperatures can promote the complete and entropically irreversible conversion of light to the fundamental mode at a target frequency.Our theoretical results are corroborated by numerical simulations in settings where second-harmonic generation,sum-frequency generation and four-wave mixing processes can manifest.展开更多
A high integrated monolithic IC, with functions of clock recovery, data decision, and 1 ： 4 demultiplexer,is implemented in 0.25μm CMOS process for 2.5Gb/s fiber-optic communications. The recovered and frequency div...A high integrated monolithic IC, with functions of clock recovery, data decision, and 1 ： 4 demultiplexer,is implemented in 0.25μm CMOS process for 2.5Gb/s fiber-optic communications. The recovered and frequency divided 625MHz clock has a phase noise of -106.26dBc/Hz at 100kHz offset in response to a 2.5Gb/s PRBS input data （2^31-1）. The 2.5Gb/s PRBS data are demultiplexed to four 625Mb/s data. The 0.97mm× 0.97mm IC consumes 550mW under a single 3.3V power supply （not including output buffers）.展开更多
基金support from the Laboratory Directed Research and Development program at the SLAC National Accelerator Laboratorythe National Science Foundation under Grant No.NSF-2011786Use of the Linac Coherent Light Source(LCLS),SLAC National Accelerator Laboratory,is supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Contract No.DE-AC02-76SF00515.
文摘The past decades have witnessed the development of new X-ray beam sources with brightness growing at a rate surpassing Moore’s law.Current and upcoming diffraction limited and fully coherent X-ray beam sources,including multi-bend achromat based synchrotron sources and high repetition rate X-ray free electron lasers,puts increasingly stringent requirements on stability and accuracy of X-ray optics systems.Parasitic motion errors at sub-micro radian scale in beam transport and beam conditioning optics can lead to significant loss of coherence and brightness delivered from source to experiment.To address this challenge,we incorporated optical metrology based on interferometric length and angle sensing and real-time correction as part of the X-ray optics motion control system.A prototype X-ray optics system was constructed following the optical layout of a tunable X-ray cavity.On-line interferometric metrology enabled dynamical feedback to a motion control system to track and compensate for motion errors.The system achieved sub-microradian scale performance,as multiple optical elements are synchronously and continuously adjusted.This first proof of principle measurement demonstrated both the potential and necessity of incorporating optical metrology as part of the motion control architecture for large scale X-ray optical systems such as monochromators,delay lines,and in particular,X-ray cavity systems to enable the next generation cavity-based X-ray free electron lasers.
基金co-supported by the National Key R&D Program of China(No.2022YFB3403500)the National Natural Science Foundation of China(No.NSFC52202460)the China Postdoctoral Science Foundation(Nos.2021M690392,2021TQ0036,and 2023TQ0031)。
文摘In the past few decades,ion engines have been widely used in deep-space propulsion and satellite station-keeping.The aim of extending the thruster lifetime is still one of the most important parts during the design stage of ion engine.As one of the core components of ion engine,the grid assembly of ion optic systems may experience long-term ion sputtering in extreme electro-thermal environments,which will eventually lead to its structural and electron-backstreaming failures.In this paper,the current studies of the grid assembly erosion process are systematically analyzed from the aspects of sputtering damage process of grid materials,numerical simulations,and measurements of erosion characteristics of grid assembly.The advantages and disadvantages of various erosion prediction models are highlighted,and the key factors and processes affecting the prediction accuracy of grid assembly erosion patterns are analyzed.Three different types of experimental methods of grid assembly erosion patterns are compared.The analysis in this paper is of great importance for selecting the sputter-resistant grid materials,as well as establishing the erosion models and measurement methods to accurately determine the erosion rate and failure modes of grid assembly.Consequently,the working conditions and structure parameters of ion optic systems could be optimized based on erosion models to promote the ion engine lifetime.
文摘We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigorous noise model of the receiver has been developed for this purpose.We calculate the total noise and sensitivity of the receiver.The front-end of the receiver exhibits a sensitivity of -45 dBm at a bit rate of 1 Gb/s and -30 dBm at a bit rate of 10 Gb/s,and the total mean-square noise curren t〈i2n〉=5×10-15 A2 at a bit rate of 1 Gb/s an d〈i2n〉 =10-12 A2 at a bit rate of 10 Gb/s,and a 3-dB bandwidth of 10 GHz.
文摘The improved three novel schemes of the super forward error correction （super-FEC） concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon（RS）＋ Bose-Chaudhuri-Hocguenghem（BCH） inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS（255,239） ＋RS（255,239） code and the RS（255,239） ＋RS（255,223） code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS（255,239） code and other codes, and their signal to noise ratio gains are respectively 2-3 dB more than that of the RS（255,239）code at the bit error rate of 1 × 10^-13. Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.
基金National High Technology Development Program(863) of China (2005AA123730) Natural Science Foundation of Chongqing University of Posts & Telecommunications(A2006 -53)
文摘A new concatenated code of RS（255,239）＋BCH（2 040,1 930） code to he suitable for WDM optical transmission systems is proposed. The simulation resuhs show that this new concatenated code. compared with the RS（255,239）4-CSOC（k0/n0=6/7, J= 8） code in ITU-TG. 75.1, has a lower redundancy and better error-correction performance, furthermore, its net coding gain（NCG） is respectively 0. 46 dB, 0.43 dB morethanthatofRS（255,239）＋CSOC（k0/n0= 6/7, J= 8） code and BCH（3860,3824）＋BCH （2 040,1 930） code in ITU TG. 75. 1 at the third iteration for the bit error rate（BER） of 10^-12. Therefore, the new super forward error correction（Super-FEC） concatenated code can be better used in ultra long-haul, ultra large-capacity and ultra high-speed WDM optical communication systems.
基金supported by the National Natural Science Foundation of China(No.61671375)the Industrial Research of Science and Technology Plan of Shaanxi Province(No.2016GY-082)
文摘Equalization can compensate channel distortion caused by channel multipath effects, and effectively improve convergent of modulation constellation diagram in optical wireless system. In this paper, the subspace blind equalization algorithm is used to preprocess M-ary phase shift keying(MPSK) subcarrier modulation signal in receiver. Mountain clustering is adopted to get the clustering centers of MPSK modulation constellation diagram, and the modulation order is automatically identified through the k-nearest neighbor(KNN) classifier. The experiment has been done under four different weather conditions. Experimental results show that the convergent of constellation diagram is improved effectively after using the subspace blind equalization algorithm, which means that the accuracy of modulation recognition is increased. The correct recognition rate of 16 PSK can be up to 85% in any kind of weather condition which is mentioned in paper. Meanwhile, the correct recognition rate is the highest in cloudy and the lowest in heavy rain condition.
基金supported by National Key Basic Research Program of China(973 Program)under Grant No.2010CB328000National Natural Science Foundation of China under Grant No.61073168,60972023,61102068+7 种基金China Postdoctoral Science Foundation funded project under Grant No.20110490389Research Fund of National Mobile Communications Research Laboratory,Southeast University under Grant No.2010A06the Open Research Fund of National Mobile Communication Research Laboratory,Southeast University under Grant No.2010D01National Science and Technology Important Special Project under Grant No.2010ZX03003-002,2010ZX03003-004the Open research fund of the State Key Laboratory of Integrated Services Networks,Xidian University under Grant No.ISN12-11NUAA Research Funding under Grant No.NS2011013the Open Research Fund of State Key Laboratory of Advance Optical Communication Systems and Networks under Grant No.2008SH06the Startup Fund of Nanjing University of Aeronautics and Astronautics and Fundation of Graduate Innovation Center in NUAA
文摘This paper investigates the performance of multi-hop Free Space Optical(FSO) communications using serial Decode-and-Forward(DF) relay transmissions.A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence-induced fading,mis alignment fading and pass-loss is presented.Under given weather and mis alignment conditions,a closed-form analytical expression for the end-to-end outage probability of serial Decode-and-Forward(DF) multi-hop FSO communications is derived.Numerical results show that the serial DF multi-hop transmission is a promising technology to enhance the performance of FSO communications.Moreover,the derived analytical expression can provide close approximations to the simulation results.
基金supported by the National Natural Science Foundation of China (Grant No. 61671347)the Fundamental ResearchFunds for the Central Universities (Grant No. 20106151859 & 20106161859)supported by 111 Project of China (B08038)
文摘In this work, the performance of free-space optical(FSO) communication system based on maximal ratio combining using binary phase shift keying subcarrier intensity modulation over Gamma-Gamma fading channels has been studied systematically. Under identically or non-identically distributed branches, the analytical expressions for the bit error rate function of signal-to-noise are derived by expressing the modified Bessel function of second kind with Meijer G-function for dualand triple-branch systems, respectively. In terms of H-fox function, the new expressions have more general forms and are more efficient for computation. It is found that the dual-and triple-branch systems significantly outperform the direct link system under weak, moderate and strong turbulence conditions. Monte Carlo simulation is also provided to confirm the accuracy of the proposed model.
基金Project supported by the National Natural Science Foundation of China (Grant No. U1930402)support from the Project Funded by China Postdoctoral Science Foundation (Grant Nos. 2020M680006 and 2021T140045)+1 种基金support from the National Natural Science Foundation of China (Grant No. 12004184)the Natural Science Foundation of Jiangsu Province, China (Grants No. BK20190428)。
文摘The contradiction between classical and quantum physics can be identified through quantum contextuality, which does not need composite systems or spacelike separation. Contextuality is proven either by a logical contradiction between the noncontextuality hidden variable predictions and those of quantum mechanics or by the violation of noncontextual inequality. We propose an experimental scheme of state-independent contextual inequality derived from the Mermin proof of the Kochen–Specker(KS) theorem in eight-dimensional Hilbert space, which could be observed either in an individual system or in a composite system. We also show how to resolve the compatibility problems. Our scheme can be implemented in optical systems with current experiment techniques.
基金RGC(ECS 24203724,YCRG C4004-24Y,YCRG C1002-22Y)NSFC(62405258)+2 种基金Innovation and Technology Fund(ITS/237/22)Innovation and TechnologyFund(ITS/226/21FP)NSFC/RGC Joint Research Scheme(N_CUHK444/22).
文摘Driven by advancements in artificial intelligence,end-to-end learning has become a key method for system optimization in various fields,including communications.However,applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature.Existing methods typically require developing a precise differentiable digital model of the physical system,which is computationally complex and can cause significant performance loss after deployment.In response,we propose a novel end-to-end learning framework called physics-guided learning.
文摘The optical noninvasive diagnostic of characteristic of silicon semiconductor devices by using a InGaAsP/InP semiconductor laser as an optical probe is reported. The principle of experimental method is based on the dependence of the optical refractive index on the carrier charge density in the active region of devices and detection of variation of refractive index by two laser beam interferometric techniques.
文摘The principle of new optical fibre pressure transducer is analysed, and ingenious design scheme of this transducer is given. This new transducer specimen is provided with following characteristics: experimental transmitting distance is 20 m (actually up to 1 000 m ); system sensitivity is 0. 1 mV/Pa; power consumption of the probe is less than 125 μW. Finally, some points of the appraisement are given in this paper.
文摘The formalism of generalized diffraction integral for paraxial misaligned optical systems is used to investigate the propagation of the Modified Bessel-Gaussian (MBG) beam through a misaligned thin lens. The properties of the propagation of MBG beam traveling through this misaligned ABCD optical system are discussed. A special case of misaligned circular thin lens is illustrated analytically and numerically. The shape of the MBG beam at the exit of the misaligned optical system is unchanged;however the center of the beam is shifted from the propagation axis in correlated manner with the design parameters of the optical system.
基金Project supported by the Program of Excellent Team in Harbin Institute of Technology,China
文摘A stable and accurate pointing,acquisition system is an important part of initially building intersatellite optical communication links.Satellite platform vibration can cause the system instability and reduce the system precision in building and maintenance of a satellite optical communication system.In this paper,vibration influence is consciously discussed by acquisition time for intersatellite optical communications.Analytical expression of acquisition possibility is derived,taking the scan parameters and platform vibration into account,and vibration influence on the multi-scan acquisition time is also presented.The theoretical result calculated by the proposed analytical expression is approximate to the result by the Monte Carlo simulation.
文摘Optical Wireless Communication(OWC)is a new trend in communication systems to achieve large bandwidth,high bit rate,high security,fast deployment,and low cost.The basic idea of the OWC is to transmit data on unguided media with light.This system requires multi-carrier modulation such as Orthogonal Frequency Division Multiplexing(OFDM).This paper studies optical OFDM performance based on Intensity Modulation with Direct Detection(IM/DD)system.This system requires a non-negativity constraint.The paper presents a framework for wireless optical OFDM system that comprises(IM/DD)with different forms,Direct Current biased Optical OFDM(DCO-OFDM),Asymmetrically Clipped Optical OFDM(ACO-OFDM),Asymmetrically DC-biased Optical OFDM(ADO-OFDM),and Flip-OFDM.It also considers channel coding as a tool for error control,channel equalization for reducing deterioration due to channel effects,and investigation of the turbulence effects.The evaluation results of the proposed framework reveal enhancement of performance.The performance of the IM/DD-OFDM system is investigated over different channel models such as AWGN,log-normal turbulence channel model,and ceiling bounce channel model.The simulation results show that the BER performance of the IM/DD-OFDM communication system is enhanced while the fading strength is decreased.The results reveal also that Hamming codes,BCH codes,and convolutional codes achieve better BER performance.Also,two algorithms of channel estimation and equalization are considered and compared.These algorithms include the Least Squares(LS)and the Minimum Mean Square Error(MMSE).The simulation results show that the MMSE algorithm gives better BER performance than the LS algorithm.
基金supported by the National Natural Science Foundation of China(Grant Nos.11274037 and 61275075)the Program for New Century Excellent Talents in University,Ministry of Education of China(Grant No.NCET-12-0765)the Foundation for the Author of National Excellent Doctoral Dissertation,China(Grant No.201236)
文摘A novel scheme of differential polarization demodulation is presented and demonstrated based on a polarized asym- metrical Mach-Zehnder interferometer configuration with polarization control. To enhance the stability of the demodulator, a phase-lock device is designed, and it is composed of a symmetric 3 × 3 coupler and a feedback circuit. For further estab- lishing a differential polarization-shift keying （DPolSK） transmission system, we successfully carry out the demodulation experiments on 10-Gb/s DPolSK optical signals for the first time. Due to the all-optical structure with phase-lock, our scheme is available to realize the DPolSK optical communication in practical optical fiber systems.
基金supported by 973 Program of China under Grant No.2006CB302900part by the National Natural Science Foundation of China under Grant No.60825405 and No.60778018
文摘Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerably high precision, but it is hard to operate from the viewpoint of operation. The method using contacting lithography technology or laser ablation can be easily operated with the cost of reducing fabrication precision and the trouble of choosing appropriate materials. For all of these methods, the coding of half tone masks with corrections for the nonlinear characteristics of coding, imaging and photoresist is recommended.
文摘Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd：YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 nm. The reorientation rate of azo polymer films is enhanced in the presence of Ag nanoparticles, and the rate of the azo polymer film with Ag concentration of 2.2 μg/ml is larger than that of the azo polymer films with Ag concentrations of 1.1 μg/ml and 4.4 μg/ml. The third-order nonlinear optical properties of the Ag/azo composite film are obtained by the Z-scan technique at a wavelength of 532 nm, and the measured nonlinear refractive index is 9.258×10-9 esu. It is shown that the main mechanisms involved in the large nonlinear optical responses come from the local field enhancement of Ag nanoparticles and the nonlinear effect of the azo polymer matrix.
基金supported by the Air Force Offce of Scientific Research(AFOSR)Multidisciplinary University Research Initiative(MURI)award on Novel light-matter interactions in topologically non-trivial Weyl semimetal structures and systems(award No.FA9550-20-1-0322)AFOSR MURI award on Programmable systems with non-Hermitian quantum dynamics(award no.FA9550-21-1-0202)+5 种基金ONR MURI award on the classical entanglement of light(award No.N00014-20-1-2789)the Army Research Offce(W911NF-23-1-0312)the Department of Energy(DE-SCo022282)W.M.Keck Foundation,the Department of Energy(DE-SCo025224),MPS Simons collaboration(Simons grant No.733682)US Air Force Research Laboratory(FA86511820019)AFRL-Applied Research Solutions(S03015)(FA8650-19-C-1692).
文摘Frequency generation in highly multimode nonlinear optical systems is inherently a complex process,giving rise to an exceedingly convoluted landscape of evolution dynamics.While predicting and controlling the global conversion efficiencies in such nonlinear environments has long been considered impossible,here,we formally address this challenge even in scenarios involving a very large number of spatial modes.By utilizing fundamental notions from optical statistical mechanics,we develop a universal theoretical framework that effectively treats all frequency components as chemical reactants/products,capable of undergoing optical thermodynamic reactions facilitated by a variety of multi-wave mixing effects.These photon-photon reactions are governed by conservation laws that directly determine the optical temperatures and chemical potentials of the ensued chemical equilibria for each frequency species.In this context,we develop a comprehensive stoichiometric model and formally derive an expression that relates the chemical potentials to the optical stoichiometric coefficients,in a manner akin to atomic/molecular chemical reactions.This advancement unlocks new predictive capabilities that can facilitate the optimization of frequency generation in highly multimode photonic arrangements,surpassing the limitations of conventional schemes that rely exclusively on nonlinear optical dynamics.Notably,we identify a universal regime of Rayleigh-Jeans thermalization where an optical reaction at near-zero optical temperatures can promote the complete and entropically irreversible conversion of light to the fundamental mode at a target frequency.Our theoretical results are corroborated by numerical simulations in settings where second-harmonic generation,sum-frequency generation and four-wave mixing processes can manifest.
文摘A high integrated monolithic IC, with functions of clock recovery, data decision, and 1 ： 4 demultiplexer,is implemented in 0.25μm CMOS process for 2.5Gb/s fiber-optic communications. The recovered and frequency divided 625MHz clock has a phase noise of -106.26dBc/Hz at 100kHz offset in response to a 2.5Gb/s PRBS input data （2^31-1）. The 2.5Gb/s PRBS data are demultiplexed to four 625Mb/s data. The 0.97mm× 0.97mm IC consumes 550mW under a single 3.3V power supply （not including output buffers）.
