BP neural network is introduced to the fault location field of DWDM optical network in this paper. The alarm characteris-tics of the optical network equipments are discussed,and alarm vector and fault vector diagrams ...BP neural network is introduced to the fault location field of DWDM optical network in this paper. The alarm characteris-tics of the optical network equipments are discussed,and alarm vector and fault vector diagrams are generated by analyzing some typical instances. A 17×14×18 BP neural network structure is constructed and trained by using MATLAB. By comparing the training performances,the best training algorithm of fault location among the three training algorithms is chosen. Numerical simulation results indicate that the sum squared error (SSE) of fault location is less than 0.01,and the processing time is less than 100 ms. This method not only well deals with the missing alarms or false alarms,but also improves the fault location accuracy and real-time ability.展开更多
In this paper,an optical pulse amplitude modulation with 4 levels(PAM-4)using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless ...In this paper,an optical pulse amplitude modulation with 4 levels(PAM-4)using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless optical communication system.Two on-off keying signals with different amplitudes are used to modulate two pigtailed laser diodes,respectively,and the generated optical signals are superimposed into optical PAM-4 signals by a fiber combiner.The optical PAM-4scheme can effectively alleviate the nonlinearity,although it reduces the peak-to-peak value of the emitting optical power by 25%.A real-time data rate of 187.5 Mbit/s is achieved by using the optical PAM-4 with a transmission distance of 50 m.The data rate is increased by about 25%compared with the conventional electrical PAM-4 in the same condition.展开更多
We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consisting of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-domain...We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consisting of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-domain numerical method.Simulation results show that the edge modes improve the electromagnetic coupling between devices. This structure works as a novel, tunable mid-infrared band-pass filter. Our studies will benefit the fabrication of planar, ultra-compact nano-scale devices in the mid-infrared region. A power splitter consisting of two output ribbons that is useful in photonic integrated devices and circuits is also designed and simulated. These devices are useful for designing ultra-compact planar devices in photonic integrated circuits.展开更多
Ground-breaking optical wireless power transfer(OWPT)techniques have gained significant attention from both academia and industry in recent decades.Powering remote systems through laser diodes(LDs)to either operate de...Ground-breaking optical wireless power transfer(OWPT)techniques have gained significant attention from both academia and industry in recent decades.Powering remote systems through laser diodes(LDs)to either operate devices or recharge batteries offers several benefits.Remote LDs can remove the burden of carrying extra batteries and can reduce mission time by removing battery swap-time and charging.Apart from its appealing benefits,laser power transfer(LPT)is still a challenging task due to its low transfer efficiency.In this paper,we discuss the necessity and feasibility of OWPT and discuss several projects,working principle,system design,and components.In addition,we show that OWPT is an essential element to supply power to Internet-of-Things(IoT)terminals.We also highlight the impacts of dynamic OWPT.We outline several OWPT techniques including optical beamforming,distributed laser charging(DLC),adaptive-DLC(ADLC),simultaneous lightwave information and power transfer(SLIPT),Thing-to-Thing(T2T)OWPT,and high intensity laser power beaming(HILPB).We also deal with laser selection,hazard analysis,and received photovoltaic(PV)cell selection for OWPT systems.Finally,we discuss a range of open challenges and counter measures.We believe that this review will be helpful in integrating research and eliminating technical uncertainties,thereby promoting progress and innovation in the development of OWPT technologies.展开更多
The integration of high-speed optical communication and distributed sensing could bring intelligent functionalities to ubiquitous optical fibre networks,such as urban structure imaging,ocean seismic detection,and safe...The integration of high-speed optical communication and distributed sensing could bring intelligent functionalities to ubiquitous optical fibre networks,such as urban structure imaging,ocean seismic detection,and safety monitoring of underground embedded pipelines.This work demonstrates a scheme of integrated sensing and communication in an optical fibre(ISAC-OF)using the same wavelength channel for simultaneous data transmission and distributed vibration sensing.The scheme not only extends the intelligent functionality for optical fibre communication system,but also improves its transmission performance.A periodic linear frequency modulation(LFM)light is generated to act as the optical carrier and sensing probe in PAM4 signal transmission and phase-sensitive optical time-domain reflectometry(Φ-OTDR),respectively.After a 24.5 km fibre transmission,the forward PAM4 signal and the carriercorrespondence Rayleigh backscattering signal are detected and demodulated.Experimental results show that the integrated solution achieves better transmission performance(~1.3 dB improvement)and a larger launching power(7 dB enhancement)at a 56 Gbit/s bit rate compared to a conventional PAM4 signal transmission.Meanwhile,a 4m spatial resolution,4.32-nε/√Hz strain resolution,and over 21 kHz frequency response for the vibration sensing are obtained.The proposed solution offers a new path to further explore the potential of existing or future fibre-optic networks by the convergence of data transmission and status sensing.In addition,such a scheme of using shared spectrum in communication and distributed optical fibre sensing may be used to measure non-linear parameters in coherent optical communications,offering possible benefits for data transmission.展开更多
Foreseeing the proliferation of underwater vehicles and sensors,underwater wireless optical communication(UWOC)is a key enabler for ocean exploration,with strong competitiveness in short-range bandwidth-intensive appl...Foreseeing the proliferation of underwater vehicles and sensors,underwater wireless optical communication(UWOC)is a key enabler for ocean exploration,with strong competitiveness in short-range bandwidth-intensive applications.We provide a tutorial on the basic concepts and essential features of UWOC,as well as an overview of work being conducted in this field.Research challenges,arising from the characteristics of underwater channels,and possible roadmaps are discussed in detail.This review is expected to be of great use for the link designers of this field.展开更多
We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof10 Gb/s/channel wavelength-division-multiplexed(WDM) passive optical network to realize a colorless optical ...We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof10 Gb/s/channel wavelength-division-multiplexed(WDM) passive optical network to realize a colorless optical network unit and bidirectional transmission over a single fiber. The modulation depth of downstream differential phase-shift keying is properly reduced to facilitate phase remodulation and Rayleigh noise mitigation. For both downstream and upstream 10 Gb/s signals, error-free transmission via a 20 km single-mode fiber is demonstrated without dispersion compensation operation.展开更多
Information leakage, which damages the transmission medium in optical communication systems, is becoming increasingly serious. The existing optical communication systems can easily expose data to unauthorized users, s...Information leakage, which damages the transmission medium in optical communication systems, is becoming increasingly serious. The existing optical communication systems can easily expose data to unauthorized users, specifically when malicious users control the target demodulator. Therefore, based on the alliance chain, the data are encrypted first based on the elliptic curve encryption algorithm and the signature algorithm, and then they are transmitted through the optical network system. Thus, a blockchain-based optical communication security transmission system scheme is proposed. The scheme has a high modulation and demodulation efficiency, fast operation speed, and verifiability. The theoretical analysis and experimental results indicate that the scheme has better security and high performance, and it generates the security requirements of optical communication systems during data transmission.展开更多
In this paper,a new two-dimensional variable weight optical orthogonal code(2D-VWOOC)for optical code division multiple access(OCDMA)system is constructed.It takes the C as the frequency hopping sequence and the stric...In this paper,a new two-dimensional variable weight optical orthogonal code(2D-VWOOC)for optical code division multiple access(OCDMA)system is constructed.It takes the C as the frequency hopping sequence and the strict variable weight optical orthogonal code(SVWOOC)as the time spreading sequence.The code can meet the different quality of service(QoS)requirements of different users.Under the same time spread sequence,the bit error rate(BER)of QCHC/SVWOOC is 3~9 orders of magnitude lower than that of other similar 2D-VWOOCs.In Optisystem simulation,when the transmission rate of the system is 14 Gbits/s,the BER of users with code weight 4 is 7 orders of magnitude lower than that of users with code weight 2,and a clear and correct eye diagram can be obtained.展开更多
Bi-doped SiO 2 –Al 2 O 3 –GeO 2 fiber preforms are prepared by modified chemical vapor deposition (MCVD) and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investig...Bi-doped SiO 2 –Al 2 O 3 –GeO 2 fiber preforms are prepared by modified chemical vapor deposition (MCVD) and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investigated, and a distinct difference in emission between the two is observed. Under 808-nm excitation, an ultra-broad near-infrared (NIR) emission with full-width at half-maximum (FWHM) of 495 nm is observed in the Bi-doped fiber. This observation, to our knowledge, is the first in this field. The NIR emission consists of two bands, which may be ascribed to the Bi 0 and Bi + species, respectively. This Bi-doped fiber is promising for broadband optical amplification and widely tunable laser.展开更多
This paper presents an improved method for imaging in turbid water by using the individual strengths of the quadrature lock-in discrimination(QLD)method and the retinex method.At first,the high-speed QLD is performed ...This paper presents an improved method for imaging in turbid water by using the individual strengths of the quadrature lock-in discrimination(QLD)method and the retinex method.At first,the high-speed QLD is performed on images,aiming at capturing the ballistic photons.Then,we perform the retinex image enhancement on the QLD-processed images to enhance the contrast of the image.Next,the effect of uneven illumination is suppressed by using the bilateral gamma function for adaptive illumination correction.The experimental results depict that the proposed approach achieves better enhancement than the existing approaches,even in a high-turbidity environment.展开更多
The selection of appropriate codes for an optical code division multiple access(OCDMA)network,which determines the maximum number of users and bit error rate(BER)supported by the system,is crucial.This study proposed ...The selection of appropriate codes for an optical code division multiple access(OCDMA)network,which determines the maximum number of users and bit error rate(BER)supported by the system,is crucial.This study proposed a variable weight zero cross-correlation Latin square(VW-ZLS)code for spectral amplitude coding(SAC)-OCDMA systems,which offers high autocorrelation and zero cross-correlation,while providing differentiated quality of service(QoS)features.Using direct detection(DD)technology,the data rate of the proposed VW-ZLS code reached 4.8 Gbit/s under the condition that BER does not exceed 10-9.This was 0.5 Gbit/s higher than that of zero cross-correlation magic square variable weight optical orthogonal code(ZMS-VWOOC)with the same cross-correlation characteristics.Further,simulation results showed that in SAC-OCDMA system,the VW-ZLS code was better than ZMS-VWOOC and exhibited excellent performance.展开更多
Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal...Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing(OFDM)modulation,based on the three-layer chaotic encryption and chaotic discrete Fourier transform(DFT)precoding.The three-layer chaotic encryption processes are bit stream diffusion,in-phase/quadrature encryption,and time-frequency scrambling.With multi-fold data encryption,the scheme can create a keyspace of 9.7×10^(179),effectively resisting brute force attacks and chosen-plaintext attacks.A 3 Gbit/s encrypted OFDM signal is successfully transmitted over a 7 m water channel.展开更多
A variable weight address code based on spectrum amplitude coding(SAC)is proposed for optical code division multiple access(OCDMA)networks to support different quality of service(Qo S)requirements of different service...A variable weight address code based on spectrum amplitude coding(SAC)is proposed for optical code division multiple access(OCDMA)networks to support different quality of service(Qo S)requirements of different services.The zero cross-correlation magic square variable weight optical orthogonal code(ZMS-VWOOC)proposed in this paper has great flexibility in terms of code weight and number of users.Zero cross-correlation can eliminate the influence of multiple access interference(MAI)and reduce the system complexity.Numerical results show that ZMS-VWOOC can provide better quality of service than similar codes.Numerical results for a ZMS-VWOOC OCDMA network designed for triple-play services operating at 0.622 Gbit/s,2 Gbit/s,2.5 Gbit/s and 3 Gbit/s are considered.展开更多
The spectral characteristics and sensitivities of a tapered two-mode fiber sandwiched between two single-mode fibers are systematically investigated. Theoretical calculations reveal that a dispersion turning point(DTP...The spectral characteristics and sensitivities of a tapered two-mode fiber sandwiched between two single-mode fibers are systematically investigated. Theoretical calculations reveal that a dispersion turning point(DTP)appears when the group effective refractive index(RI) difference between the fundamental mode and the higher-order mode equals zero;as a result, ultrahigh RI sensitivities can be achieved. Furthermore, the location of the DTP is strongly dependent on the tapering condition. Then, we experimentally demonstrate high sensitivities of the RI sensor with the waist diameter of 4 μm by means of immersing it in a flow cell filled with glycerol solution. In further tracking of the resonant wavelength shift around the DTP, it is found that the proposed RI sensor exhibits a sensitivity of 1.81 × 104 nm/RIU and a limit of detection down up to 3.29 × 10-5 RIU in a liquid glycerol solution.展开更多
Multicore fibers are expected to be a game-changer in the coming decades thanks to their intrinsic properties,allowing a larger transmission bandwidth and a lower footprint in optical communications.In addition,multic...Multicore fibers are expected to be a game-changer in the coming decades thanks to their intrinsic properties,allowing a larger transmission bandwidth and a lower footprint in optical communications.In addition,multicore fibers have recently been explored for quantum communication,attesting to their uniqueness in transporting high-dimensional quantum states.However,investigations and experiments reported in literature have been carried out in research laboratories,typically making use of short fiber links in controlled environments.Thus,the possibility of using long-distance multicore fibers for quantum applications is still to be proven.We characterize here for the first time,to the best of our knowledge,in terms of phase stability,multiple strands of a four-core multicore fiber installed underground in the city of L’Aquila,with an overall fiber length up to about 25 km.In this preliminary study,we investigate the possibility of using such an infrastructure to implement quantumenhanced schemes,such as high-dimensional quantum key distribution,quantum-based environmental sensors,and more,in general,quantum communication protocols.展开更多
文摘BP neural network is introduced to the fault location field of DWDM optical network in this paper. The alarm characteris-tics of the optical network equipments are discussed,and alarm vector and fault vector diagrams are generated by analyzing some typical instances. A 17×14×18 BP neural network structure is constructed and trained by using MATLAB. By comparing the training performances,the best training algorithm of fault location among the three training algorithms is chosen. Numerical simulation results indicate that the sum squared error (SSE) of fault location is less than 0.01,and the processing time is less than 100 ms. This method not only well deals with the missing alarms or false alarms,but also improves the fault location accuracy and real-time ability.
基金supported by the National Natural Science Foundation of China(NSFC)(No.61971378)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030208)Zhoushan-Zhejiang University Joint Research Project(No.2019C81081)。
文摘In this paper,an optical pulse amplitude modulation with 4 levels(PAM-4)using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless optical communication system.Two on-off keying signals with different amplitudes are used to modulate two pigtailed laser diodes,respectively,and the generated optical signals are superimposed into optical PAM-4 signals by a fiber combiner.The optical PAM-4scheme can effectively alleviate the nonlinearity,although it reduces the peak-to-peak value of the emitting optical power by 25%.A real-time data rate of 187.5 Mbit/s is achieved by using the optical PAM-4 with a transmission distance of 50 m.The data rate is increased by about 25%compared with the conventional electrical PAM-4 in the same condition.
文摘We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consisting of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-domain numerical method.Simulation results show that the edge modes improve the electromagnetic coupling between devices. This structure works as a novel, tunable mid-infrared band-pass filter. Our studies will benefit the fabrication of planar, ultra-compact nano-scale devices in the mid-infrared region. A power splitter consisting of two output ribbons that is useful in photonic integrated devices and circuits is also designed and simulated. These devices are useful for designing ultra-compact planar devices in photonic integrated circuits.
文摘Ground-breaking optical wireless power transfer(OWPT)techniques have gained significant attention from both academia and industry in recent decades.Powering remote systems through laser diodes(LDs)to either operate devices or recharge batteries offers several benefits.Remote LDs can remove the burden of carrying extra batteries and can reduce mission time by removing battery swap-time and charging.Apart from its appealing benefits,laser power transfer(LPT)is still a challenging task due to its low transfer efficiency.In this paper,we discuss the necessity and feasibility of OWPT and discuss several projects,working principle,system design,and components.In addition,we show that OWPT is an essential element to supply power to Internet-of-Things(IoT)terminals.We also highlight the impacts of dynamic OWPT.We outline several OWPT techniques including optical beamforming,distributed laser charging(DLC),adaptive-DLC(ADLC),simultaneous lightwave information and power transfer(SLIPT),Thing-to-Thing(T2T)OWPT,and high intensity laser power beaming(HILPB).We also deal with laser selection,hazard analysis,and received photovoltaic(PV)cell selection for OWPT systems.Finally,we discuss a range of open challenges and counter measures.We believe that this review will be helpful in integrating research and eliminating technical uncertainties,thereby promoting progress and innovation in the development of OWPT technologies.
基金supported by the National Key Research and Development Program of China(2019YFB1803500)the National Natural Science Foundation of China(NSFC)(61735015,61860206006,62205275,62005228).
文摘The integration of high-speed optical communication and distributed sensing could bring intelligent functionalities to ubiquitous optical fibre networks,such as urban structure imaging,ocean seismic detection,and safety monitoring of underground embedded pipelines.This work demonstrates a scheme of integrated sensing and communication in an optical fibre(ISAC-OF)using the same wavelength channel for simultaneous data transmission and distributed vibration sensing.The scheme not only extends the intelligent functionality for optical fibre communication system,but also improves its transmission performance.A periodic linear frequency modulation(LFM)light is generated to act as the optical carrier and sensing probe in PAM4 signal transmission and phase-sensitive optical time-domain reflectometry(Φ-OTDR),respectively.After a 24.5 km fibre transmission,the forward PAM4 signal and the carriercorrespondence Rayleigh backscattering signal are detected and demodulated.Experimental results show that the integrated solution achieves better transmission performance(~1.3 dB improvement)and a larger launching power(7 dB enhancement)at a 56 Gbit/s bit rate compared to a conventional PAM4 signal transmission.Meanwhile,a 4m spatial resolution,4.32-nε/√Hz strain resolution,and over 21 kHz frequency response for the vibration sensing are obtained.The proposed solution offers a new path to further explore the potential of existing or future fibre-optic networks by the convergence of data transmission and status sensing.In addition,such a scheme of using shared spectrum in communication and distributed optical fibre sensing may be used to measure non-linear parameters in coherent optical communications,offering possible benefits for data transmission.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61971378 and61671409)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030208)+1 种基金the National Key Research and Development Program of China(Nos.2016YFC1401202,2017YFC0306601,and 2017YFC0306100)the Fundamental Research Funds for the Central Universities
文摘Foreseeing the proliferation of underwater vehicles and sensors,underwater wireless optical communication(UWOC)is a key enabler for ocean exploration,with strong competitiveness in short-range bandwidth-intensive applications.We provide a tutorial on the basic concepts and essential features of UWOC,as well as an overview of work being conducted in this field.Research challenges,arising from the characteristics of underwater channels,and possible roadmaps are discussed in detail.This review is expected to be of great use for the link designers of this field.
基金partly supported by the National Natural Science Foundation of China(Nos.61301141 and61671409)the Sichuan Provincial Science and Technology Project(No.2014GZ0015)the Sichuan Provincial Department of Education Project(No.15TD0050)
文摘We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof10 Gb/s/channel wavelength-division-multiplexed(WDM) passive optical network to realize a colorless optical network unit and bidirectional transmission over a single fiber. The modulation depth of downstream differential phase-shift keying is properly reduced to facilitate phase remodulation and Rayleigh noise mitigation. For both downstream and upstream 10 Gb/s signals, error-free transmission via a 20 km single-mode fiber is demonstrated without dispersion compensation operation.
基金supported by the Guangxi Science and Technology Program(Nos.AB17292082 and AB18126025)。
文摘Information leakage, which damages the transmission medium in optical communication systems, is becoming increasingly serious. The existing optical communication systems can easily expose data to unauthorized users, specifically when malicious users control the target demodulator. Therefore, based on the alliance chain, the data are encrypted first based on the elliptic curve encryption algorithm and the signature algorithm, and then they are transmitted through the optical network system. Thus, a blockchain-based optical communication security transmission system scheme is proposed. The scheme has a high modulation and demodulation efficiency, fast operation speed, and verifiability. The theoretical analysis and experimental results indicate that the scheme has better security and high performance, and it generates the security requirements of optical communication systems during data transmission.
基金This work has been supported by the Guangxi S&T Program(Nos.AB17292082 and AB18126025).
文摘In this paper,a new two-dimensional variable weight optical orthogonal code(2D-VWOOC)for optical code division multiple access(OCDMA)system is constructed.It takes the C as the frequency hopping sequence and the strict variable weight optical orthogonal code(SVWOOC)as the time spreading sequence.The code can meet the different quality of service(QoS)requirements of different users.Under the same time spread sequence,the bit error rate(BER)of QCHC/SVWOOC is 3~9 orders of magnitude lower than that of other similar 2D-VWOOCs.In Optisystem simulation,when the transmission rate of the system is 14 Gbits/s,the BER of users with code weight 4 is 7 orders of magnitude lower than that of users with code weight 2,and a clear and correct eye diagram can be obtained.
文摘Bi-doped SiO 2 –Al 2 O 3 –GeO 2 fiber preforms are prepared by modified chemical vapor deposition (MCVD) and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investigated, and a distinct difference in emission between the two is observed. Under 808-nm excitation, an ultra-broad near-infrared (NIR) emission with full-width at half-maximum (FWHM) of 495 nm is observed in the Bi-doped fiber. This observation, to our knowledge, is the first in this field. The NIR emission consists of two bands, which may be ascribed to the Bi 0 and Bi + species, respectively. This Bi-doped fiber is promising for broadband optical amplification and widely tunable laser.
基金supported in part by the National Key Research and Development Program of China(Nos.2022YFC2808200 and 2022YFB2903403)the National Natural Science Foundation of China(NSFC)(No.61971378)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030208).
文摘This paper presents an improved method for imaging in turbid water by using the individual strengths of the quadrature lock-in discrimination(QLD)method and the retinex method.At first,the high-speed QLD is performed on images,aiming at capturing the ballistic photons.Then,we perform the retinex image enhancement on the QLD-processed images to enhance the contrast of the image.Next,the effect of uneven illumination is suppressed by using the bilateral gamma function for adaptive illumination correction.The experimental results depict that the proposed approach achieves better enhancement than the existing approaches,even in a high-turbidity environment.
基金supported by the Guangxi Science and Technology Program(No.AB18126025).
文摘The selection of appropriate codes for an optical code division multiple access(OCDMA)network,which determines the maximum number of users and bit error rate(BER)supported by the system,is crucial.This study proposed a variable weight zero cross-correlation Latin square(VW-ZLS)code for spectral amplitude coding(SAC)-OCDMA systems,which offers high autocorrelation and zero cross-correlation,while providing differentiated quality of service(QoS)features.Using direct detection(DD)technology,the data rate of the proposed VW-ZLS code reached 4.8 Gbit/s under the condition that BER does not exceed 10-9.This was 0.5 Gbit/s higher than that of zero cross-correlation magic square variable weight optical orthogonal code(ZMS-VWOOC)with the same cross-correlation characteristics.Further,simulation results showed that in SAC-OCDMA system,the VW-ZLS code was better than ZMS-VWOOC and exhibited excellent performance.
基金supported by the National Natural Science Foundation of China(NSFC)(No.61971378)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030208)Zhoushan-Zhejiang University Joint Research Project(No.2019C81081)。
文摘Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing(OFDM)modulation,based on the three-layer chaotic encryption and chaotic discrete Fourier transform(DFT)precoding.The three-layer chaotic encryption processes are bit stream diffusion,in-phase/quadrature encryption,and time-frequency scrambling.With multi-fold data encryption,the scheme can create a keyspace of 9.7×10^(179),effectively resisting brute force attacks and chosen-plaintext attacks.A 3 Gbit/s encrypted OFDM signal is successfully transmitted over a 7 m water channel.
基金supported by the Guangxi S&T Program(Nos.AB17292082 and AB18126025)。
文摘A variable weight address code based on spectrum amplitude coding(SAC)is proposed for optical code division multiple access(OCDMA)networks to support different quality of service(Qo S)requirements of different services.The zero cross-correlation magic square variable weight optical orthogonal code(ZMS-VWOOC)proposed in this paper has great flexibility in terms of code weight and number of users.Zero cross-correlation can eliminate the influence of multiple access interference(MAI)and reduce the system complexity.Numerical results show that ZMS-VWOOC can provide better quality of service than similar codes.Numerical results for a ZMS-VWOOC OCDMA network designed for triple-play services operating at 0.622 Gbit/s,2 Gbit/s,2.5 Gbit/s and 3 Gbit/s are considered.
基金supported by the National Natural Science Foundation of China(No.61505119)the National Postdoctoral Program for Innovative Talents(No.BX201600077)+2 种基金the Brain Gain Foundation of Nanjing University of Posts and Telecommunications(No.NY215040)the China Postdoctoral Science Foundation(No.2017M611877)the Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province(No.GD201706)
文摘The spectral characteristics and sensitivities of a tapered two-mode fiber sandwiched between two single-mode fibers are systematically investigated. Theoretical calculations reveal that a dispersion turning point(DTP)appears when the group effective refractive index(RI) difference between the fundamental mode and the higher-order mode equals zero;as a result, ultrahigh RI sensitivities can be achieved. Furthermore, the location of the DTP is strongly dependent on the tapering condition. Then, we experimentally demonstrate high sensitivities of the RI sensor with the waist diameter of 4 μm by means of immersing it in a flow cell filled with glycerol solution. In further tracking of the resonant wavelength shift around the DTP, it is found that the proposed RI sensor exhibits a sensitivity of 1.81 × 104 nm/RIU and a limit of detection down up to 3.29 × 10-5 RIU in a liquid glycerol solution.
基金orizon 2020 Framework Programme OpenQKD(857156),SQUARE(731473)Ministero dell’Istruzione,dell’Universitàe della Ricerca(INCIPIT)+1 种基金H2020 Science with and for Society(G5485)Danmarks Grundforskningsfond SPOC(123).
文摘Multicore fibers are expected to be a game-changer in the coming decades thanks to their intrinsic properties,allowing a larger transmission bandwidth and a lower footprint in optical communications.In addition,multicore fibers have recently been explored for quantum communication,attesting to their uniqueness in transporting high-dimensional quantum states.However,investigations and experiments reported in literature have been carried out in research laboratories,typically making use of short fiber links in controlled environments.Thus,the possibility of using long-distance multicore fibers for quantum applications is still to be proven.We characterize here for the first time,to the best of our knowledge,in terms of phase stability,multiple strands of a four-core multicore fiber installed underground in the city of L’Aquila,with an overall fiber length up to about 25 km.In this preliminary study,we investigate the possibility of using such an infrastructure to implement quantumenhanced schemes,such as high-dimensional quantum key distribution,quantum-based environmental sensors,and more,in general,quantum communication protocols.
