The phase-sensitive optical time-domain reflectometry(φ-OTDR)is a good candidate for distributed dynamic strain sensing,due to its high sensitivity and fast measurement,which has already been widely used in intrusion...The phase-sensitive optical time-domain reflectometry(φ-OTDR)is a good candidate for distributed dynamic strain sensing,due to its high sensitivity and fast measurement,which has already been widely used in intrusion monitoring,geophysical exploration,etc.For the frequency scanning basedφ-OTDR,the phase change manifests itself as a shift of the intensity distribution.The correlation between the reference and measured spectra is employed for relative strain demodulation,which has imposed the continuous measurement for the absolute strain demodulation.Fortunately,the Brillouin optical time domain analysis(BOTDA)allows for the absolute strain demodulation with only one measurement.In this work,the combination of theφ-OTDR and BOTDA has been proposed and demonstrated by using the same set of frequency-scanning optical pulses,and the frequency-agile technique is also introduced for fast measurements.A 9.9 Hz vibration with a strain range of 500 nεhas been measured under two different absolute strains(296.7μεand 554.8με)by integrating the Rayleigh and Brillouin information.The sub-micro strain vibration is demonstrated by theφ-OTDR signal with a high sensitivity of 6.8 nε,while the absolute strain is measured by the BOTDA signal with an accuracy of 5.4με.The proposed sensor allows for dynamic absolute strain measurements with a high sensitivity,thus opening a door for new possibilities which are yet to be explored.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
Optical chirp chain Brillouin optical time-domain analysis(OCC-BOTDA) has the capabilities of fast measurement, high Brillouin threshold, and freedom from the nonlocal effect;at the same time, however, it also has pro...Optical chirp chain Brillouin optical time-domain analysis(OCC-BOTDA) has the capabilities of fast measurement, high Brillouin threshold, and freedom from the nonlocal effect;at the same time, however, it also has problems introduced by transient stimulated Brillouin scattering. The influence of the transient interaction is reflected as the broadened asymmetric Brillouin spectrum, the ghost peak, and the frequency shift of the main peak. This introduces difficulty in computing the fiber Brillouin frequency shift with good measurement accuracy. Besides, the OCC modulation causes additional noise due to the uneven amplitude response for different frequency components. In this work, we propose a high-performance OCC-BOTDA using the principal component analysis(PCA) based pattern recognition algorithm and differential pulse-width pair(DPP) technique.After building the Brillouin spectrum database(i.e., all patterns), the fiber intrinsic Brillouin frequency shift can be recognized by the PCA algorithm from a nonstandard Brillouin spectrum profile, resulting in good measurement accuracy. Meanwhile, the DPP technique, subtracting between two Brillouin signals generated by two wide-width pump pulses, is utilized to reduce the OCC modulation noise and avoid the pulse self-phase modulation effect in long-range BOTDA sensing. In the experiment, a temperature measurement with 1.3 MHz measurement precision, 4 m spatial resolution, and 5 s measurement time is achieved over a 100 km single-mode fiber.展开更多
A 100-J-level Nd:glass laser system in nanosecond-scale pulse width has been constructed to perform as a standard source of high-fluence-laser science experiments. The laser system, operating with typical pulse durati...A 100-J-level Nd:glass laser system in nanosecond-scale pulse width has been constructed to perform as a standard source of high-fluence-laser science experiments. The laser system, operating with typical pulse durations of 3–5 ns and beam diameter 60 mm, employs a sequence of successive rod amplifiers to achieve 100-J-level energy at 1053 nm at3 ns. The frequency conversion can provide energy of 50-J level at 351 nm. In addition to the high stability of the energy output, the most valuable of the laser system is the high spatiotemporal beam quality of the output, which contains the uniform square pulse waveform, the uniform flat-top spatial fluence distribution and the uniform flat-top wavefront.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
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(61975045)The authors would like to express our gratitude to Long Wang,Chao Pang and Yabo Feng for their help in the experiment.
文摘The phase-sensitive optical time-domain reflectometry(φ-OTDR)is a good candidate for distributed dynamic strain sensing,due to its high sensitivity and fast measurement,which has already been widely used in intrusion monitoring,geophysical exploration,etc.For the frequency scanning basedφ-OTDR,the phase change manifests itself as a shift of the intensity distribution.The correlation between the reference and measured spectra is employed for relative strain demodulation,which has imposed the continuous measurement for the absolute strain demodulation.Fortunately,the Brillouin optical time domain analysis(BOTDA)allows for the absolute strain demodulation with only one measurement.In this work,the combination of theφ-OTDR and BOTDA has been proposed and demonstrated by using the same set of frequency-scanning optical pulses,and the frequency-agile technique is also introduced for fast measurements.A 9.9 Hz vibration with a strain range of 500 nεhas been measured under two different absolute strains(296.7μεand 554.8με)by integrating the Rayleigh and Brillouin information.The sub-micro strain vibration is demonstrated by theφ-OTDR signal with a high sensitivity of 6.8 nε,while the absolute strain is measured by the BOTDA signal with an accuracy of 5.4με.The proposed sensor allows for dynamic absolute strain measurements with a high sensitivity,thus opening a door for new possibilities which are yet to be explored.
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National Natural Science Foundation of China(NSFC)(61575052)National Key Scientific Instrument and Equipment Development Project of China(2017YFF0108700)
文摘Optical chirp chain Brillouin optical time-domain analysis(OCC-BOTDA) has the capabilities of fast measurement, high Brillouin threshold, and freedom from the nonlocal effect;at the same time, however, it also has problems introduced by transient stimulated Brillouin scattering. The influence of the transient interaction is reflected as the broadened asymmetric Brillouin spectrum, the ghost peak, and the frequency shift of the main peak. This introduces difficulty in computing the fiber Brillouin frequency shift with good measurement accuracy. Besides, the OCC modulation causes additional noise due to the uneven amplitude response for different frequency components. In this work, we propose a high-performance OCC-BOTDA using the principal component analysis(PCA) based pattern recognition algorithm and differential pulse-width pair(DPP) technique.After building the Brillouin spectrum database(i.e., all patterns), the fiber intrinsic Brillouin frequency shift can be recognized by the PCA algorithm from a nonstandard Brillouin spectrum profile, resulting in good measurement accuracy. Meanwhile, the DPP technique, subtracting between two Brillouin signals generated by two wide-width pump pulses, is utilized to reduce the OCC modulation noise and avoid the pulse self-phase modulation effect in long-range BOTDA sensing. In the experiment, a temperature measurement with 1.3 MHz measurement precision, 4 m spatial resolution, and 5 s measurement time is achieved over a 100 km single-mode fiber.
基金supported by the project of the National Natural Science Foundation of China (grant numbers 61378007 and 61138005)
文摘A 100-J-level Nd:glass laser system in nanosecond-scale pulse width has been constructed to perform as a standard source of high-fluence-laser science experiments. The laser system, operating with typical pulse durations of 3–5 ns and beam diameter 60 mm, employs a sequence of successive rod amplifiers to achieve 100-J-level energy at 1053 nm at3 ns. The frequency conversion can provide energy of 50-J level at 351 nm. In addition to the high stability of the energy output, the most valuable of the laser system is the high spatiotemporal beam quality of the output, which contains the uniform square pulse waveform, the uniform flat-top spatial fluence distribution and the uniform flat-top wavefront.
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.