The distributed sensor is proven to be a powerful tool for civil structural and material process monitoring. Brillouin scattering in fiber can be used as point sensors or distributed sensors for measurement of tempera...The distributed sensor is proven to be a powerful tool for civil structural and material process monitoring. Brillouin scattering in fiber can be used as point sensors or distributed sensors for measurement of temperature, strain, birefringence and vibration over centimeters （Brillouin grating length） for point sensor or the pulse length for the distributed sensor. Simultaneous strain and temperature measurement with a spatial resolution of 20 cm is demonstrated in a Panda fiber using Brillouin grating technique with the temperature accuracy and strain accuracy of 0.4 ℃ and 9 με. This technique can also be used for distributed birefringence measurement. For Brillouin optical time domain analysis （BOTDA）, we have developed a new technique to measure differential Brillouin gain instead of Brillouin gain itself. This technique allows high precision temperature and strain measurement over long sensing length with sub-meter spatial resolution： 50-cm spatial resolution for 50-km length, using return-to-zero coded optical pulses of BOTDA with the temperature resolution of 0.7 ℃, which is equivalent to strain accuracy of 12 με. For over 50-km sensing length, we proposed and demonstrated frequency-division-multiplexing （FDM） and time-division-multiplexing （TDM） based BOTDA technique for 75-km and 100-km sensing length without inline amplification within the sensing length. The spatial resolution of 2m （100km） and Brillouin frequency shift accuracy of 1.5 MHz have been obtained for TDM based BOTDA and 1-m resolution （75 km） with Brillouin frequency shift accuracy of 1 MHz using FDM based BOTDA. The civil structural health monitoring with BOTDA technique has been demonstrated.展开更多
A highly accurate,fully analytic solution for the continuous wave and the probe wave in Brillouin amplification,in lossless optical fibers,is given.It is experimentally confirmed that the reported analytic solution ca...A highly accurate,fully analytic solution for the continuous wave and the probe wave in Brillouin amplification,in lossless optical fibers,is given.It is experimentally confirmed that the reported analytic solution can account for spectral distortion and pump depletion in the parameter space that is relevant to Brillouin fiber sensor applications,as well as applications in photonic logic.The analytic solutions are valid characterizations of Brillouin amplification in both the low and high nonlinearity regime,for short fiber lengths.展开更多
Precise control and measurement of the optical fiber diameter are vital for a range of fields,such as ultra-high sensitivity sensing and high-speed optical communication.Nowadays,the measurement of fiber diameter reli...Precise control and measurement of the optical fiber diameter are vital for a range of fields,such as ultra-high sensitivity sensing and high-speed optical communication.Nowadays,the measurement of fiber diameter relies on point measurement schemes such as microscopes,which suffer from a tradeoff between the resolution and field of view.Handling the fiber can irreversibly damage the fiber samples,especially when multi-point measurements are required.To overcome these problems,we have explored a novel technique in which the mechanical properties of fibers are reflected by forward stimulated Brillouin scattering(FSBS),from which the diameters can be demodulated via the acoustic dispersion relation.The distributed FSBS spectra with narrow linewidths were recorded via the optimized optomechanical time-domain analysis system using coherent FSBS,thereby achieving a spatial resolution of 1 m over a fiber length of tens of meters.We successfully obtained the diameter distribution of unjacketed test fibers with diameters of 125μm and 80μm.The diameter accuracy was verified by high-quality scanning electron microscope images.We achieved a diameter resolution of 3.9 nm,virtually independent of the diameter range.To the best of our knowledge,this is the first demonstration of non-destructive and distributed fiber diameter monitoring with nanometer resolution.展开更多
Brillouin optical time-domain analysis(BOTDA)requires frequency mapping of the Brillouin spectrum to obtain environmental information(e.g.,temperature or strain)over the length of the sensing fiber,with the finite fre...Brillouin optical time-domain analysis(BOTDA)requires frequency mapping of the Brillouin spectrum to obtain environmental information(e.g.,temperature or strain)over the length of the sensing fiber,with the finite frequencysweeping time-limiting applications to only static or slowly varying strain or temperature environments.To solve this problem,we propose the use of an optical chirp chain probe wave to remove the requirement of frequency sweeping for the Brillouin spectrum,which enables distributed ultrafast strain measurement with a single pump pulse.The optical chirp chain is generated using a frequency-agile technique via a fast-frequency-changing microwave,which covers a larger frequency range around the Stokes frequency relative to the pump wave,so that a distributed Brillouin gain spectrum along the fiber is realized.Dynamic strain measurements for periodic mechanical vibration,mechanical shock,and a switch event are demonstrated at sampling rates of 25 kHz,2.5 MHz and 6.25 MHz,respectively.To the best of our knowledge,this is the first demonstration of distributed Brillouin strain sensing with a wide-dynamic range at a sampling rate of up to the MHz level.展开更多
Distributed optical fiber sensors have been widely used to monitor temperature, strain, vibration, and so on. Specifically, the sensors based on Brillouin scattering have been studied extensively to measure the strain...Distributed optical fiber sensors have been widely used to monitor temperature, strain, vibration, and so on. Specifically, the sensors based on Brillouin scattering have been studied extensively to measure the strain or temperature along an oDtical fiber.展开更多
文摘The distributed sensor is proven to be a powerful tool for civil structural and material process monitoring. Brillouin scattering in fiber can be used as point sensors or distributed sensors for measurement of temperature, strain, birefringence and vibration over centimeters （Brillouin grating length） for point sensor or the pulse length for the distributed sensor. Simultaneous strain and temperature measurement with a spatial resolution of 20 cm is demonstrated in a Panda fiber using Brillouin grating technique with the temperature accuracy and strain accuracy of 0.4 ℃ and 9 με. This technique can also be used for distributed birefringence measurement. For Brillouin optical time domain analysis （BOTDA）, we have developed a new technique to measure differential Brillouin gain instead of Brillouin gain itself. This technique allows high precision temperature and strain measurement over long sensing length with sub-meter spatial resolution： 50-cm spatial resolution for 50-km length, using return-to-zero coded optical pulses of BOTDA with the temperature resolution of 0.7 ℃, which is equivalent to strain accuracy of 12 με. For over 50-km sensing length, we proposed and demonstrated frequency-division-multiplexing （FDM） and time-division-multiplexing （TDM） based BOTDA technique for 75-km and 100-km sensing length without inline amplification within the sensing length. The spatial resolution of 2m （100km） and Brillouin frequency shift accuracy of 1.5 MHz have been obtained for TDM based BOTDA and 1-m resolution （75 km） with Brillouin frequency shift accuracy of 1 MHz using FDM based BOTDA. The civil structural health monitoring with BOTDA technique has been demonstrated.
文摘A highly accurate,fully analytic solution for the continuous wave and the probe wave in Brillouin amplification,in lossless optical fibers,is given.It is experimentally confirmed that the reported analytic solution can account for spectral distortion and pump depletion in the parameter space that is relevant to Brillouin fiber sensor applications,as well as applications in photonic logic.The analytic solutions are valid characterizations of Brillouin amplification in both the low and high nonlinearity regime,for short fiber lengths.
基金This work was supported by the National Key Scientific Instrument and Equipment Development Project of China(2017YFF0108700)National Natural Science Foundation of China(62005067)+2 种基金National Postdoctoral Program for Innovative Talents(BX20200104)China Postdoctoral Science Foundation(2020M681088)the Heilongjiang Postdoctoral Fund to pursue scientific research(LBH-Z20067).
文摘Precise control and measurement of the optical fiber diameter are vital for a range of fields,such as ultra-high sensitivity sensing and high-speed optical communication.Nowadays,the measurement of fiber diameter relies on point measurement schemes such as microscopes,which suffer from a tradeoff between the resolution and field of view.Handling the fiber can irreversibly damage the fiber samples,especially when multi-point measurements are required.To overcome these problems,we have explored a novel technique in which the mechanical properties of fibers are reflected by forward stimulated Brillouin scattering(FSBS),from which the diameters can be demodulated via the acoustic dispersion relation.The distributed FSBS spectra with narrow linewidths were recorded via the optimized optomechanical time-domain analysis system using coherent FSBS,thereby achieving a spatial resolution of 1 m over a fiber length of tens of meters.We successfully obtained the diameter distribution of unjacketed test fibers with diameters of 125μm and 80μm.The diameter accuracy was verified by high-quality scanning electron microscope images.We achieved a diameter resolution of 3.9 nm,virtually independent of the diameter range.To the best of our knowledge,this is the first demonstration of non-destructive and distributed fiber diameter monitoring with nanometer resolution.
基金supported by the National Key Scientific Instrument and Equipment Development Project of China(2017YFF0108700)National Natural Science Foundation of China(61575052)。
文摘Brillouin optical time-domain analysis(BOTDA)requires frequency mapping of the Brillouin spectrum to obtain environmental information(e.g.,temperature or strain)over the length of the sensing fiber,with the finite frequencysweeping time-limiting applications to only static or slowly varying strain or temperature environments.To solve this problem,we propose the use of an optical chirp chain probe wave to remove the requirement of frequency sweeping for the Brillouin spectrum,which enables distributed ultrafast strain measurement with a single pump pulse.The optical chirp chain is generated using a frequency-agile technique via a fast-frequency-changing microwave,which covers a larger frequency range around the Stokes frequency relative to the pump wave,so that a distributed Brillouin gain spectrum along the fiber is realized.Dynamic strain measurements for periodic mechanical vibration,mechanical shock,and a switch event are demonstrated at sampling rates of 25 kHz,2.5 MHz and 6.25 MHz,respectively.To the best of our knowledge,this is the first demonstration of distributed Brillouin strain sensing with a wide-dynamic range at a sampling rate of up to the MHz level.
基金supported by the National Natural Science Foundation of China(Nos.61377089 and 61527819)the International Science&Technology Cooperation Program of China(No.2014DFA50870)the Natural Science Foundation of Shanxi(Nos.2015011049 and201601D021069)
文摘Distributed optical fiber sensors have been widely used to monitor temperature, strain, vibration, and so on. Specifically, the sensors based on Brillouin scattering have been studied extensively to measure the strain or temperature along an oDtical fiber.
