The integrated optical true time delay phased array antenna system has the advantages of high bandwidth,small size,low loss and strong antiinterference capability,etc.The high integration of the optically controlled p...The integrated optical true time delay phased array antenna system has the advantages of high bandwidth,small size,low loss and strong antiinterference capability,etc.The high integration of the optically controlled phased array antenna system is a necessary trend for the future development of the phased array,and it is also a major focus and difficulty in the current research of integrated microwave photonics.This paper firstly introduces the basic principle and development history of optical true time delay phased array antenna system based on microwave photonics,and briefly introduces the main implementation methods and integration platform of optical true time delay.Then,the application and development prospect of optical true time delay technology in beam control of phased array antenna system are mainly presented.Finally,according to the current research progress,the possible research directions of integrated optically controlled phased array antenna systems in the future are proposed.展开更多
The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry （BOTDR） are investigated numerically and experimentally. Simulation results show that the spectral linewi...The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry （BOTDR） are investigated numerically and experimentally. Simulation results show that the spectral linewidth of spontaneous Brillouin scattering remains almost constant when the laser linewidth is less than 1 MHz at the same pulse width; otherwise, it increases sharply. A comparison between a fiber laser （FL） with 4-kHz linewidth at 3 dB and a distributed feedback （DFB） laser with 3-MHz linewidth is made experimentally. When a constant laser power is launched into the sensing fiber, the fitting linewidths of the beat signals （backscattered Brillouin light and local oscillator （LO）） is about 5 MHz wider for the DFB laser than for the FL and the intensity of the beat signal is about a half. Furthermore, the frequency fluctuation in the long sensing fiber is lower for the FL source, yielding about 2 MHz less than that of the DFB laser, indicating higher temperature/strain resolution. The experimental results are in good agreement with the numerical simulations.展开更多
The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensi...The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card （DAQ）. A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator （LO） in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio （SNR） has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement.展开更多
The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is...The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is presented. The influence of quantum fluctuation can be effectively controlled by demodulation technology since quantum fluctuation shows a uniform distribution in the frequency domain. Combined with the changing of the integration time of the lock-in amplifier, the signal to noise ratio is significantly enhanced. Accordingly the signal to noise improvement ratio reaches 31.7 dB compared with the direct photon counting measurement.展开更多
Optical Time Division Multiplexing （OTDM） is known to be capable of transmitting single channel high bit rate data stream with low speed electro-optical components. A cost-effective, compact and stable short time wi...Optical Time Division Multiplexing （OTDM） is known to be capable of transmitting single channel high bit rate data stream with low speed electro-optical components. A cost-effective, compact and stable short time window with low insert loss, low phase noise, low timing-jitter and high speed performance is essential for ultra-high speed OTDM systems using phase and amplitude modulation formats. In this paper, we review three promising methods to obtain 40 GHz short time window including Electro-Absorption Modulator （EAM）, Dual-Parallel Mach-Zehnder Modulator （DPMZM） and Fiber Loop-Polarization Modulator （FL-PolM）. Sub-picosecond short pulse source generation, optical time division denlaltiplexing and clock recovery are realized respectively by using the short time window based on the three methods. By using DPMZM based pulse source and EAM based Clock Recovery （CR） and dermltiplexer, error free transmission of 640 Goit/s （160 Gbaud/s Pol-Mux DQPSK） single channel signal over 400 km single mode fiber is proven to be experimentally successful.展开更多
Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The prin...Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The principle of the proposed technique to reduce the fading noise is introduced based on the analysis of Rayleigh Brillouin optical time domain analysis system. The experimental results show that the signal-to-noise ratio(SNR) at the end of optical fiber with length of 50 m after 17 times wavelength scanning is 5.21 d B higher than that with single wavelength, the Brillouin frequency shift(BFS) on the heated fiber with length of 70 m inserted at the center of sensing fiber can be accurately measured as 0.19 MHz, which is equivalent to a measurement accuracy of 0.19 °C. It indicates that the proposed technique can realize high-accuracy temperature measurement and has huge potential in the field of long-distance and high-accuracy sensing.展开更多
An environmentally friendly,low power consuming,sensitive and compact mercury analyzer was developed for the determination of mercury in water samples by integrating a thin film dielectric barrier discharge induced co...An environmentally friendly,low power consuming,sensitive and compact mercury analyzer was developed for the determination of mercury in water samples by integrating a thin film dielectric barrier discharge induced cold vapor reactor and a dielectric barrier discharge optical emission spectrometer into a small polymethyl methacrylate plate（10.5 cm length×8.0 cm width×1.2 cm height）.Mercury cold vapor was generated when standard or sample solutions with or without formic acid were introduced to the reactor to form thin film liquid and exposed to microplasma irradiation and subsequently separated from the liquid phase for transport to the microplasma and detection of its atomic emission.Limits of detection of 0.20 μg L^-1 and 2.6 μg L^-1 were obtained for the proposed system using or not using formic acid,respectively.Compared to the conventional microplasma optical emission spectrometry used for mercury analysis,this system not only retains the good limit of detection amenable to the determination of mercury in real samples,but also reduces power consumption,eliminates the generation of hydrogen and avoids the use of toxic or unstable reductant.Method validation was demonstrated by analysis of a certified reference material of water sample and three real water samples with good spike recoveries（88-102%）.展开更多
A novel optical analog-to-digital converter based on optical time division multiplexing(OTDM) is described which uses electrooptic sampling and time-demultiplexing together with multiple electronic analog-to-digital c...A novel optical analog-to-digital converter based on optical time division multiplexing(OTDM) is described which uses electrooptic sampling and time-demultiplexing together with multiple electronic analog-to-digital converter(ADC). Compared with the previous scheme, the time-division multiplexer and the time-division demultiplexer are applied in the optical analog-to-digital converter(OADC) at the same time, the design of the OADC is simplified and the performance of the OADC based on time-division demultiplexer is improved. A core optical part of the system is demonstrated with a sample rate of 10 Gs/s. The signals in three channels are demultiplexed from the optical pulses.The result proves our scheme is feasible.展开更多
Time-slotted optical burst switched network is a potential technique to support IP over Wavelength Division Multiplexing (WDM) by introduce Time Division Multiplexing (TDM) channel to Optical Burst Switching (OBS) tec...Time-slotted optical burst switched network is a potential technique to support IP over Wavelength Division Multiplexing (WDM) by introduce Time Division Multiplexing (TDM) channel to Optical Burst Switching (OBS) technology. This paper presents a framework to evaluate blocking performance of time-slot-ted OBS networks with multi-fiber wavelength channels. The proposed model is efficient for not only single class traffic such as individual circuit switch traffics or best-effort traffics but also mixed multi-class traffics. The effectiveness of the proposed model is validated by simulation results. The study shows that blocking per-formance of multi-fiber TS-OBS network is acceptable for future Internet services.展开更多
Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency t...Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer,measurement of fundamental physical constants,and high-precision ranging,achieving a series of milestone results in ground-based environments.With the continuous maturation and evolution of femtosecond lasers and related technologies,optical frequency combs are moving from ground-based applications to astronomical and space-based applications,playing an increasingly important role in atomic clocks,exoplanet observations,gravitational wave measurements,and other areas.This paper,focusing on astronomical and space-based applications,reviews research progress on astronomical frequency combs,optical clock time-frequency networks,gravitational waves,dark matter measurement,dual-comb large-scale absolute ranging,and high-resolution atmospheric spectroscopy.With enhanced performance and their gradual application in the field of space-based research,optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.展开更多
Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods...Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.展开更多
A novel chaotic optical time-domain reflectometry(OTDR)-based approach was proposed for monitoring long-haul fiber communication systems with multiple fiber segments. The self-phase modulation and group velocity dispe...A novel chaotic optical time-domain reflectometry(OTDR)-based approach was proposed for monitoring long-haul fiber communication systems with multiple fiber segments. The self-phase modulation and group velocity dispersion effects of the optical cable was considered in demonstrating the proof-of-concept experiment and simulation. In experiments, the correlation peaks are clearly obtained from the correlation trace between the reference and reflected(or scattered) light signals propagating in three optical-fiber segments. The technique affords a high spatial resolution of 2 m, and further long-haul fiber simulations indicate that the sensing distance can be more than 3300 km. Thus, the new proposed technique can be effectively applied for health monitoring of long-haul fiber communication systems.展开更多
Landslide risk is increasing in many parts of the world due to growth of population and infrastructures. Therefore, an effort has to be made in developing new and cheap sensors for areas susceptible of landslides to c...Landslide risk is increasing in many parts of the world due to growth of population and infrastructures. Therefore, an effort has to be made in developing new and cheap sensors for areas susceptible of landslides to continuously control the slope behaviour, until approaching failure conditions. The paper reported experimental data from smallscale physical models about the performance of Time Domain Reflectometry(TDR) and optical fibres, which act as the indicators of the incoming failure of slopes covered by unsaturated granular soils. Obtained results appear encouraging, since both sensors provide continuous information about the state of the slope, in terms of water content profiles and ongoing deformations, induced by rainwater infiltration, even immediately before the triggering of a fast landslide.展开更多
A novel laser-assisted pulsed plasma thruster(LA-PPT)is proposed as an electric propulsion thruster,which separates laser ablation and electromagnetic acceleration.It aims for a higher specific impulse than that achie...A novel laser-assisted pulsed plasma thruster(LA-PPT)is proposed as an electric propulsion thruster,which separates laser ablation and electromagnetic acceleration.It aims for a higher specific impulse than that achieved with conventional LA-PPTs.Owing to the short-time discharge and the novel configuration,the physical mechanism of the discharge is unclear.Time and spatial-resolved optical emission spectroscopy was applied to investigate the variation in the plasma properties in the thruster discharge channel.The plasma species,electron temperature,and electron density were obtained and discussed.Our investigation revealed that there were H_(α),H_(β),H_(γ),H_(ε) atoms,CⅠ,CⅡ,CⅢ,CⅣ,ClⅠ,ClⅡparticles,and a small amount of CH,C_(3),C_(2),H_(2) neutral molecular groups in the plasma.The electron temperature of the discharge channel of the thruster was within 0.6–4.9 e V,and the electron density was within(1.1–3.0)×10^(18)cm^(-3),which shows that the optical emission spectroscopy method is to measure the electron excitation temperature and electron density in heavy particles.But the Langmuir probe method is to measure the temperature and density of free electrons.The use of laser instead of spark plug as the ignition mode significantly changed the plasma distribution in the discharge channel.Unlike the conventional PPT,which has high electron density near the thruster surface,LAPPT showed relatively large electron density at the thruster outlet,which increased the thruster specific impulse.In addition,the change in the ignition mode enabled the electron density in the LA-PPT discharge channel to be higher than that in the conventional PPT.This proves that the ignition mode with laser replacing the spark plug effectively optimised the PPT performance.展开更多
As a fiber sensor, optical time domain L reflectometer becomes more and more popular to measure parameters, such as strain and temperature in structural health monitoring （SHM） simultaneously. Since the accuracy of...As a fiber sensor, optical time domain L reflectometer becomes more and more popular to measure parameters, such as strain and temperature in structural health monitoring （SHM） simultaneously. Since the accuracy of range resolution in optical time domain reflectometer （OTDR） is determined by the pulse width of laser, the range resolution in order of centimeter is achieved by employing of picoseconds lasers which are not commercial. In this paper, to achieve this accuracy with conventional OTDR, Fourier wavelet regularized deconvolution （ForWaRD） method is employed to deconvolve and denoise the detected signal simultaneously. Simulations show that this method improves resolution of conventional OTDR system to the order of several centimeters.展开更多
Distributed fiber-optic sensing has become an indispensable tool for large-scale structural and environmentalmonitoring, where spectral interrogation of backscattering light enables high-precision quantitative measure...Distributed fiber-optic sensing has become an indispensable tool for large-scale structural and environmentalmonitoring, where spectral interrogation of backscattering light enables high-precision quantitative measurement ofexternal perturbations. Conventional spectral analysis methods, typically based on frequency-domain serialinterrogation or time-to-frequency mapping, face inherent trade-offs between measurement speed, dynamic strainmeasurement range, and system complexity. Here, we present a distributed frequency comb enabled spectrumcorrelationreflectometry as a universal spectral analysis framework that leverages optical frequency comb for parallelmulti-frequency interrogation, which is experimentally demonstrated in a phase-sensitive optical time-domainreflectometry (φ-OTDR) system. This method eliminates the need for large frequency scans, achieving more thantenfold improvement in measurement speed over the state-of-the-art spectral analysis methods. Compared to existingphase-demodulated φ-OTDR systems, this method enables vibration amplitude monitoring with a dynamic strainmeasurement range expanded by more than an order of magnitude, while intrinsically circumventing phaseunwrapping issues and interference fading. This work establishes a new paradigm for distributed spectral analysis,providing a flexible and robust platform for a wide range of sensing technologies, including Rayleigh and Brillouinbasedschemes, which may have significant impact for geophysics, seismology, civil engineering, and other fields.展开更多
Phase-sensitive optical time domain reflectometry(Ф-OTDR)is an effective way to detect vibrations and acoustic waves with high sensitivity,by interrogating coherent Rayleigh backscattering light in sensing fiber.In p...Phase-sensitive optical time domain reflectometry(Ф-OTDR)is an effective way to detect vibrations and acoustic waves with high sensitivity,by interrogating coherent Rayleigh backscattering light in sensing fiber.In particular,fiber-optic distributed acoustic sensing(DAS)based on theФ-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection,borehole seismic acquisition,structure health monitoring,etc.,in recent years,with superior advantages such as long sensing range,fast response speed,wide sensing bandwidth,low operation cost and long service lifetime.Significant advances in research and development(R&D)ofФ-OTDR have been made since 2014.In this review,we present a historical review ofФ-OTDR and then summarize the recent progress ofФ-OTDR in the Fiber Optics Research Center(FORC)at University of Electronic Science and Technology of China(UESTC),which is the first group to carry out R&D ofФ-OTDR and invent ultra-sensitive DAS(uDAS)seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019.It can be seen that theФ-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.展开更多
A brief review of recent progress in researches, productions and applications of full distributed fiber Raman photon sensors at China Jiliang University （CJLU） is presented. In order to improve the measurement dista...A brief review of recent progress in researches, productions and applications of full distributed fiber Raman photon sensors at China Jiliang University （CJLU） is presented. In order to improve the measurement distance, the accuracy, the space resolution, the ability of multi-parameter measurements, and the intelligence of full distributed fiber sensor systems, a new generation fiber sensor technology based on the optical fiber nonlinear scattering fusion principle is proposed. A series of new generation full distributed fiber sensors are investigated and designed, which consist of new generation ultra-long distance full distributed fiber Raman and Rayleigh scattering photon sensors integrated with a fiber Raman amplifier, auto-correction full distributed fiber Raman photon temperature sensors based on Raman correlation dual sources, full distributed fiber Raman photon temperature sensors based on a pulse coding source, full distributed fiber Raman photon temperature sensors using a fiber Raman wavelength shifter, a new type of Brillouin optical time domain analyzers （BOTDAs） integrated with a fiber Raman amplifier for replacing a fiber Brillouin amplifier, full distributed fiber Raman and Brillouin photon sensors integrated with a fiber Raman amplifier, and full distributed fiber Brillouin photon sensors integrated with a fiber Brillouin frequency shifter. The Internet of things is believed as one of candidates of the next technological revolution, which has driven hundreds of millions of class markets. Sensor networks are important components of the Internet of things. The full distributed optical fiber sensor network （Rayleigh, Raman, and Brillouin scattering） is a 3S （smart materials, smart structure, and smart skill） system, which is easy to construct smart fiber sensor networks. The distributed optical fiber sensor can be embedded in the power grids, railways, bridges, tunnels, roads, constructions, water supply systems, dams, oil and gas pipelines and other facilities, and can be integrated with wireless networks.展开更多
We demonstrate a distributed optical fiber sensing system based on the Michelson interferometer of the phase sensitive optical time domain reflectometer （q0-OTDR） for acoustic measurement. Phase, amplitude, frequenc...We demonstrate a distributed optical fiber sensing system based on the Michelson interferometer of the phase sensitive optical time domain reflectometer （q0-OTDR） for acoustic measurement. Phase, amplitude, frequency response, and location information can be directly obtained at the same time by using the passive 3 ×3 coupler demodulation. We also set an experiment and successfully restore the acoustic information. Meanwhile, our system has preliminary realized acoustic-phase sensitivity around -150 dB （re rad/μPa） in the experiment.展开更多
基金supported by Fund of State Key Laboratory of IPOC(BUPT)(No.IPOC2021ZT16),China.
文摘The integrated optical true time delay phased array antenna system has the advantages of high bandwidth,small size,low loss and strong antiinterference capability,etc.The high integration of the optically controlled phased array antenna system is a necessary trend for the future development of the phased array,and it is also a major focus and difficulty in the current research of integrated microwave photonics.This paper firstly introduces the basic principle and development history of optical true time delay phased array antenna system based on microwave photonics,and briefly introduces the main implementation methods and integration platform of optical true time delay.Then,the application and development prospect of optical true time delay technology in beam control of phased array antenna system are mainly presented.Finally,according to the current research progress,the possible research directions of integrated optically controlled phased array antenna systems in the future are proposed.
基金the National High Technology Research and Development Program of China(Grant No.2012AA041203)the Science and Technology Commission of Shanghai Municipality,China(Grant No.13XD1425400)the Pudong New Area Science and Technology Development Fund,China(Grant No.PKJ2012-D04)
文摘The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry （BOTDR） are investigated numerically and experimentally. Simulation results show that the spectral linewidth of spontaneous Brillouin scattering remains almost constant when the laser linewidth is less than 1 MHz at the same pulse width; otherwise, it increases sharply. A comparison between a fiber laser （FL） with 4-kHz linewidth at 3 dB and a distributed feedback （DFB） laser with 3-MHz linewidth is made experimentally. When a constant laser power is launched into the sensing fiber, the fitting linewidths of the beat signals （backscattered Brillouin light and local oscillator （LO）） is about 5 MHz wider for the DFB laser than for the FL and the intensity of the beat signal is about a half. Furthermore, the frequency fluctuation in the long sensing fiber is lower for the FL source, yielding about 2 MHz less than that of the DFB laser, indicating higher temperature/strain resolution. The experimental results are in good agreement with the numerical simulations.
基金supported by the National High Technology Research and Development Program of China(Grant No.2012AA041203)the National Natural Science Foundation of China(Grant Nos.61377062 and 31201377)+1 种基金the Program of Shanghai Excellent Technical Leaders,China(Grant No.13XD1425400)the Doctorial Fund of Zhengzhou University of Light Industry,China(Grant No.2013BSJJ012)
文摘The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card （DAQ）. A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator （LO） in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio （SNR） has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674086 and 10934004)the National Natural Science Foundation for Excellent Research Team (Grant No. 60821004)+2 种基金the National Key Basic Research and Development Program of China (Grant No. 2010CB923103)the National High Technology Research and Development Program of China (Grant No. 2009AA01Z319)the Program for Top Science and Technology Innovation Teams and Top Young and Middleaged Innovative Talents of Shanxi Province
文摘The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is presented. The influence of quantum fluctuation can be effectively controlled by demodulation technology since quantum fluctuation shows a uniform distribution in the frequency domain. Combined with the changing of the integration time of the lock-in amplifier, the signal to noise ratio is significantly enhanced. Accordingly the signal to noise improvement ratio reaches 31.7 dB compared with the direct photon counting measurement.
基金Acknowledgements This paper was partially supported by the Hi-Tech Research andDevelopment Program of China under Grant No. 2012AA011303 the National Natural Science Foundation of China under Crants No. 61001121, No. 60932004, No. 61006041+1 种基金 the National Key Basic Research Program of China under Grant No. 2011CB301702 the Fundamental Research Funds for the Central Universities.
文摘Optical Time Division Multiplexing （OTDM） is known to be capable of transmitting single channel high bit rate data stream with low speed electro-optical components. A cost-effective, compact and stable short time window with low insert loss, low phase noise, low timing-jitter and high speed performance is essential for ultra-high speed OTDM systems using phase and amplitude modulation formats. In this paper, we review three promising methods to obtain 40 GHz short time window including Electro-Absorption Modulator （EAM）, Dual-Parallel Mach-Zehnder Modulator （DPMZM） and Fiber Loop-Polarization Modulator （FL-PolM）. Sub-picosecond short pulse source generation, optical time division denlaltiplexing and clock recovery are realized respectively by using the short time window based on the three methods. By using DPMZM based pulse source and EAM based Clock Recovery （CR） and dermltiplexer, error free transmission of 640 Goit/s （160 Gbaud/s Pol-Mux DQPSK） single channel signal over 400 km single mode fiber is proven to be experimentally successful.
基金supported by the National Natural Science Foundation of China(No.61377088)the Natural Science Foundation of Hebei Province of China(Nos.E2015502053 and F2015502059)the Fundamental Research Funds for the Central Universities(No.2016XS104)
文摘Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The principle of the proposed technique to reduce the fading noise is introduced based on the analysis of Rayleigh Brillouin optical time domain analysis system. The experimental results show that the signal-to-noise ratio(SNR) at the end of optical fiber with length of 50 m after 17 times wavelength scanning is 5.21 d B higher than that with single wavelength, the Brillouin frequency shift(BFS) on the heated fiber with length of 70 m inserted at the center of sensing fiber can be accurately measured as 0.19 MHz, which is equivalent to a measurement accuracy of 0.19 °C. It indicates that the proposed technique can realize high-accuracy temperature measurement and has huge potential in the field of long-distance and high-accuracy sensing.
基金the National Natural Science Foundation of China(No.21575092)for financial support
文摘An environmentally friendly,low power consuming,sensitive and compact mercury analyzer was developed for the determination of mercury in water samples by integrating a thin film dielectric barrier discharge induced cold vapor reactor and a dielectric barrier discharge optical emission spectrometer into a small polymethyl methacrylate plate（10.5 cm length×8.0 cm width×1.2 cm height）.Mercury cold vapor was generated when standard or sample solutions with or without formic acid were introduced to the reactor to form thin film liquid and exposed to microplasma irradiation and subsequently separated from the liquid phase for transport to the microplasma and detection of its atomic emission.Limits of detection of 0.20 μg L^-1 and 2.6 μg L^-1 were obtained for the proposed system using or not using formic acid,respectively.Compared to the conventional microplasma optical emission spectrometry used for mercury analysis,this system not only retains the good limit of detection amenable to the determination of mercury in real samples,but also reduces power consumption,eliminates the generation of hydrogen and avoids the use of toxic or unstable reductant.Method validation was demonstrated by analysis of a certified reference material of water sample and three real water samples with good spike recoveries（88-102%）.
文摘A novel optical analog-to-digital converter based on optical time division multiplexing(OTDM) is described which uses electrooptic sampling and time-demultiplexing together with multiple electronic analog-to-digital converter(ADC). Compared with the previous scheme, the time-division multiplexer and the time-division demultiplexer are applied in the optical analog-to-digital converter(OADC) at the same time, the design of the OADC is simplified and the performance of the OADC based on time-division demultiplexer is improved. A core optical part of the system is demonstrated with a sample rate of 10 Gs/s. The signals in three channels are demultiplexed from the optical pulses.The result proves our scheme is feasible.
基金Founded by the National Natural Science Foundation of China (No.60502005).
文摘Time-slotted optical burst switched network is a potential technique to support IP over Wavelength Division Multiplexing (WDM) by introduce Time Division Multiplexing (TDM) channel to Optical Burst Switching (OBS) technology. This paper presents a framework to evaluate blocking performance of time-slot-ted OBS networks with multi-fiber wavelength channels. The proposed model is efficient for not only single class traffic such as individual circuit switch traffics or best-effort traffics but also mixed multi-class traffics. The effectiveness of the proposed model is validated by simulation results. The study shows that blocking per-formance of multi-fiber TS-OBS network is acceptable for future Internet services.
基金support of the National Natural Sci-ence Foundation of China(NSFC)(62305373)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA1502040404,XDB2101040004).
文摘Optical frequency combs,as powerful tools for precision spectroscopy and research into optical frequency standards,have driven continuous progress and significant breakthroughs in applications such as time-frequency transfer,measurement of fundamental physical constants,and high-precision ranging,achieving a series of milestone results in ground-based environments.With the continuous maturation and evolution of femtosecond lasers and related technologies,optical frequency combs are moving from ground-based applications to astronomical and space-based applications,playing an increasingly important role in atomic clocks,exoplanet observations,gravitational wave measurements,and other areas.This paper,focusing on astronomical and space-based applications,reviews research progress on astronomical frequency combs,optical clock time-frequency networks,gravitational waves,dark matter measurement,dual-comb large-scale absolute ranging,and high-resolution atmospheric spectroscopy.With enhanced performance and their gradual application in the field of space-based research,optical frequency combs will undoubtedly provide more powerful support for astronomical science and cosmic exploration in the future.
基金The authors gratefully acknowledge the financial support pro-vided by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.41907232)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the State Key Program of National Natural Science Foundation of China(Grant No.41230636).
文摘Anti-slide piles are one of the most important reinforcement structures against landslides,and evalu-ating the working conditions is of great significance for landslide mitigation.The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method.However,due to many assumptions involved in calculation,the analytical models cannot be fully applicable to complex site situations,e.g.landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein.In view of this,the combination of distributed fiber optic sensing(DFOS)and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area,China.Brillouin optical time domain reflectometry(BOTDR)was utilized to monitor the strain distri-bution along the pile.Next,by analyzing the relative deformation between the pile and its adjacent inclinometer,the pile-soil interface separation was profiled.Finally,the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method.According to the ratio of calculated internal forces to the design values,the working conditions of the anti-slide pile could be evaluated.The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system,and can quantitatively evaluate its working conditions.
基金the Project Funding National Natural Science Foundation of China (NSFC) (61527819)University Natural Science Research Project of Jiangsu Province (19KJB510005)High-Level Training Fund project of Nanjing Xiaozhuang University (2019NXY18)
文摘A novel chaotic optical time-domain reflectometry(OTDR)-based approach was proposed for monitoring long-haul fiber communication systems with multiple fiber segments. The self-phase modulation and group velocity dispersion effects of the optical cable was considered in demonstrating the proof-of-concept experiment and simulation. In experiments, the correlation peaks are clearly obtained from the correlation trace between the reference and reflected(or scattered) light signals propagating in three optical-fiber segments. The technique affords a high spatial resolution of 2 m, and further long-haul fiber simulations indicate that the sensing distance can be more than 3300 km. Thus, the new proposed technique can be effectively applied for health monitoring of long-haul fiber communication systems.
基金partially supported by the project Safe Land "Living with landslide risk in Europe: Assessment, effects of global change, and risk management strategies" under Grant No. 226479 (7th Framework Programme)
文摘Landslide risk is increasing in many parts of the world due to growth of population and infrastructures. Therefore, an effort has to be made in developing new and cheap sensors for areas susceptible of landslides to continuously control the slope behaviour, until approaching failure conditions. The paper reported experimental data from smallscale physical models about the performance of Time Domain Reflectometry(TDR) and optical fibres, which act as the indicators of the incoming failure of slopes covered by unsaturated granular soils. Obtained results appear encouraging, since both sensors provide continuous information about the state of the slope, in terms of water content profiles and ongoing deformations, induced by rainwater infiltration, even immediately before the triggering of a fast landslide.
基金supported by National Natural Science Foundation of China(No.11772354)。
文摘A novel laser-assisted pulsed plasma thruster(LA-PPT)is proposed as an electric propulsion thruster,which separates laser ablation and electromagnetic acceleration.It aims for a higher specific impulse than that achieved with conventional LA-PPTs.Owing to the short-time discharge and the novel configuration,the physical mechanism of the discharge is unclear.Time and spatial-resolved optical emission spectroscopy was applied to investigate the variation in the plasma properties in the thruster discharge channel.The plasma species,electron temperature,and electron density were obtained and discussed.Our investigation revealed that there were H_(α),H_(β),H_(γ),H_(ε) atoms,CⅠ,CⅡ,CⅢ,CⅣ,ClⅠ,ClⅡparticles,and a small amount of CH,C_(3),C_(2),H_(2) neutral molecular groups in the plasma.The electron temperature of the discharge channel of the thruster was within 0.6–4.9 e V,and the electron density was within(1.1–3.0)×10^(18)cm^(-3),which shows that the optical emission spectroscopy method is to measure the electron excitation temperature and electron density in heavy particles.But the Langmuir probe method is to measure the temperature and density of free electrons.The use of laser instead of spark plug as the ignition mode significantly changed the plasma distribution in the discharge channel.Unlike the conventional PPT,which has high electron density near the thruster surface,LAPPT showed relatively large electron density at the thruster outlet,which increased the thruster specific impulse.In addition,the change in the ignition mode enabled the electron density in the LA-PPT discharge channel to be higher than that in the conventional PPT.This proves that the ignition mode with laser replacing the spark plug effectively optimised the PPT performance.
文摘As a fiber sensor, optical time domain L reflectometer becomes more and more popular to measure parameters, such as strain and temperature in structural health monitoring （SHM） simultaneously. Since the accuracy of range resolution in optical time domain reflectometer （OTDR） is determined by the pulse width of laser, the range resolution in order of centimeter is achieved by employing of picoseconds lasers which are not commercial. In this paper, to achieve this accuracy with conventional OTDR, Fourier wavelet regularized deconvolution （ForWaRD） method is employed to deconvolve and denoise the detected signal simultaneously. Simulations show that this method improves resolution of conventional OTDR system to the order of several centimeters.
基金supported by the National Key R&D Program of China(2023YFB2906303)Major Program(JD)of Hubei Province(2023BAA013)+1 种基金the National Natural Science Foundation of China(62105111,62225110)the Chilean National Agency for Research and Development(Fondecyt Regular 1241085,Fondequip EQM220113 and Basal AFB240002).
文摘Distributed fiber-optic sensing has become an indispensable tool for large-scale structural and environmentalmonitoring, where spectral interrogation of backscattering light enables high-precision quantitative measurement ofexternal perturbations. Conventional spectral analysis methods, typically based on frequency-domain serialinterrogation or time-to-frequency mapping, face inherent trade-offs between measurement speed, dynamic strainmeasurement range, and system complexity. Here, we present a distributed frequency comb enabled spectrumcorrelationreflectometry as a universal spectral analysis framework that leverages optical frequency comb for parallelmulti-frequency interrogation, which is experimentally demonstrated in a phase-sensitive optical time-domainreflectometry (φ-OTDR) system. This method eliminates the need for large frequency scans, achieving more thantenfold improvement in measurement speed over the state-of-the-art spectral analysis methods. Compared to existingphase-demodulated φ-OTDR systems, this method enables vibration amplitude monitoring with a dynamic strainmeasurement range expanded by more than an order of magnitude, while intrinsically circumventing phaseunwrapping issues and interference fading. This work establishes a new paradigm for distributed spectral analysis,providing a flexible and robust platform for a wide range of sensing technologies, including Rayleigh and Brillouinbasedschemes, which may have significant impact for geophysics, seismology, civil engineering, and other fields.
基金The authors would like to thank all of the members in the FORC at UESTC for their hard work and important contributions to this workThis work was funded by the Natural Science Foundation of China(Grant Nos.41527805 and 61635005)the 111 Poject(Grant No.B14039).
文摘Phase-sensitive optical time domain reflectometry(Ф-OTDR)is an effective way to detect vibrations and acoustic waves with high sensitivity,by interrogating coherent Rayleigh backscattering light in sensing fiber.In particular,fiber-optic distributed acoustic sensing(DAS)based on theФ-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection,borehole seismic acquisition,structure health monitoring,etc.,in recent years,with superior advantages such as long sensing range,fast response speed,wide sensing bandwidth,low operation cost and long service lifetime.Significant advances in research and development(R&D)ofФ-OTDR have been made since 2014.In this review,we present a historical review ofФ-OTDR and then summarize the recent progress ofФ-OTDR in the Fiber Optics Research Center(FORC)at University of Electronic Science and Technology of China(UESTC),which is the first group to carry out R&D ofФ-OTDR and invent ultra-sensitive DAS(uDAS)seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019.It can be seen that theФ-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.
文摘A brief review of recent progress in researches, productions and applications of full distributed fiber Raman photon sensors at China Jiliang University （CJLU） is presented. In order to improve the measurement distance, the accuracy, the space resolution, the ability of multi-parameter measurements, and the intelligence of full distributed fiber sensor systems, a new generation fiber sensor technology based on the optical fiber nonlinear scattering fusion principle is proposed. A series of new generation full distributed fiber sensors are investigated and designed, which consist of new generation ultra-long distance full distributed fiber Raman and Rayleigh scattering photon sensors integrated with a fiber Raman amplifier, auto-correction full distributed fiber Raman photon temperature sensors based on Raman correlation dual sources, full distributed fiber Raman photon temperature sensors based on a pulse coding source, full distributed fiber Raman photon temperature sensors using a fiber Raman wavelength shifter, a new type of Brillouin optical time domain analyzers （BOTDAs） integrated with a fiber Raman amplifier for replacing a fiber Brillouin amplifier, full distributed fiber Raman and Brillouin photon sensors integrated with a fiber Raman amplifier, and full distributed fiber Brillouin photon sensors integrated with a fiber Brillouin frequency shifter. The Internet of things is believed as one of candidates of the next technological revolution, which has driven hundreds of millions of class markets. Sensor networks are important components of the Internet of things. The full distributed optical fiber sensor network （Rayleigh, Raman, and Brillouin scattering） is a 3S （smart materials, smart structure, and smart skill） system, which is easy to construct smart fiber sensor networks. The distributed optical fiber sensor can be embedded in the power grids, railways, bridges, tunnels, roads, constructions, water supply systems, dams, oil and gas pipelines and other facilities, and can be integrated with wireless networks.
基金This work was supported by the Shandong Natural Science Foundation （No. ZR2013FL028）, Science and Technology Development Project of Shandong Province （2014GGX 103019）, and Innovation and Achievement Transformation Projects of Shandong Province （2014ZZCX04206）.
文摘We demonstrate a distributed optical fiber sensing system based on the Michelson interferometer of the phase sensitive optical time domain reflectometer （q0-OTDR） for acoustic measurement. Phase, amplitude, frequency response, and location information can be directly obtained at the same time by using the passive 3 ×3 coupler demodulation. We also set an experiment and successfully restore the acoustic information. Meanwhile, our system has preliminary realized acoustic-phase sensitivity around -150 dB （re rad/μPa） in the experiment.
