光热干涉(photothermal interference,PTI)法是一种气体检测的新型光学方法,因其高灵敏度、高精度和“零背景”的优点,有望在油中溶解气体分析(dissolved gas analysis,DGA)检测领域中得以推广和应用。然而,油中溶解气体的温度和压强对...光热干涉(photothermal interference,PTI)法是一种气体检测的新型光学方法,因其高灵敏度、高精度和“零背景”的优点,有望在油中溶解气体分析(dissolved gas analysis,DGA)检测领域中得以推广和应用。然而,油中溶解气体的温度和压强对光热相位的影响规律尚不明确,为提高PTI技术在DGA领域的适用性,文中提出一种基于Herriott气室的光强调制型PTI油中乙炔传感方案。为模拟故障状态下变压器油中气体检测,文中对含乙炔等多组分特征气体的混合气体进行实测,并重点研究测量过程中温度和压强对检测结果的影响规律,得出温度降低和压强增大均会使光热相位增大。由此表明,乙炔检测的精度和稳定性依赖于检测过程中合理设置温度和压强。所研制的测量系统对乙炔浓度具有较强的线性响应,检测灵敏度为0.151 mV/(μL·L^(-1)),检测下限为5.3μL/L。所提方案为后续开发基于PTI技术的新型DGA检测提供了思路并奠定了基础。展开更多
High accuracy and time resolution optical transfer delay(OTD)measurement is highly desired in many multi-path applications,such as optical true-time-delay-based array systems and distributed optical sensors.However,th...High accuracy and time resolution optical transfer delay(OTD)measurement is highly desired in many multi-path applications,such as optical true-time-delay-based array systems and distributed optical sensors.However,the time resolution is usually limited by the frequency range of the probe signal in frequency-multiplexed OTD measurement techniques.Here,we proposed a time-resolution enhanced OTD measurement method based on incoherent optical frequency domain reflectometry(I-OFDR),where an adaptive filter is designed to suppress the spectral leakage from other paths to break the resolution limitation.A weighted least square(WLS)cost function is first established,and then an iteration approach is used to minimize the cost function.Finally,the appropriate filter parameter is obtained according to the convergence results.In a proof-of-concept experiment,the time-domain response of two optical links with a length difference of 900 ps is successfully estimated by applying a probe signal with a bandwidth of 400 MHz.The time resolution is improved by 2.78times compared to the theoretical resolution limit of the inverse discrete Fourier transform(iDFT)algorithm.In addition,the OTD measurement error is below±0.8 ps.The proposed algorithm provides a novel way to improve the measurement resolution without applying a probe signal with a large bandwidth,avoiding measurement errors induced by the dispersion effect.展开更多
Optoelectronic components and subsystems such as optically controlled phased array antennas,distributed radar networks,interferometric optical fiber hydrophones,and high-speed optoelectronic chips demand highaccuracy ...Optoelectronic components and subsystems such as optically controlled phased array antennas,distributed radar networks,interferometric optical fiber hydrophones,and high-speed optoelectronic chips demand highaccuracy optical time delay measurement with large measurement range and the capability for single-end and wavelength-dependent measurement.In this paper,the recent advances in the optical time delay measurement of a fiber link with high accuracy are reviewed.The general models of the typical time delay measurement technologies are established with the operational principle analyzed.The performance of these techniques is also discussed.展开更多
We demonstrate microwave photonic radar with post-bandwidth synthesis, which can realize target detection with ultra-high range resolution using relatively small-bandwidth radio frequency(RF) frontends. In the propose...We demonstrate microwave photonic radar with post-bandwidth synthesis, which can realize target detection with ultra-high range resolution using relatively small-bandwidth radio frequency(RF) frontends. In the proposed radar, two temporal-overlapped linear frequency-modulated(LFM) signals with the same chirp rate and different center frequencies are transmitted. By post-processing the de-chirped echoes in the receiver, a signal equivalent to that de-chirped from an LFM signal with the combined bandwidth is achieved. In a proof-ofconcept experiment, two LFM signals with bandwidths of 8.4 GHz are exploited to achieve radar detection with an equivalent bandwidth of 16 GHz, and a range resolution of 1 cm is obtained.展开更多
文摘光热干涉(photothermal interference,PTI)法是一种气体检测的新型光学方法,因其高灵敏度、高精度和“零背景”的优点,有望在油中溶解气体分析(dissolved gas analysis,DGA)检测领域中得以推广和应用。然而,油中溶解气体的温度和压强对光热相位的影响规律尚不明确,为提高PTI技术在DGA领域的适用性,文中提出一种基于Herriott气室的光强调制型PTI油中乙炔传感方案。为模拟故障状态下变压器油中气体检测,文中对含乙炔等多组分特征气体的混合气体进行实测,并重点研究测量过程中温度和压强对检测结果的影响规律,得出温度降低和压强增大均会使光热相位增大。由此表明,乙炔检测的精度和稳定性依赖于检测过程中合理设置温度和压强。所研制的测量系统对乙炔浓度具有较强的线性响应,检测灵敏度为0.151 mV/(μL·L^(-1)),检测下限为5.3μL/L。所提方案为后续开发基于PTI技术的新型DGA检测提供了思路并奠定了基础。
基金supported by the National Natural Science Foundation of China(Nos.62075095 and 62271249)the Key Research and Development Program of Jiangsu Province(No.BE2020030)。
文摘High accuracy and time resolution optical transfer delay(OTD)measurement is highly desired in many multi-path applications,such as optical true-time-delay-based array systems and distributed optical sensors.However,the time resolution is usually limited by the frequency range of the probe signal in frequency-multiplexed OTD measurement techniques.Here,we proposed a time-resolution enhanced OTD measurement method based on incoherent optical frequency domain reflectometry(I-OFDR),where an adaptive filter is designed to suppress the spectral leakage from other paths to break the resolution limitation.A weighted least square(WLS)cost function is first established,and then an iteration approach is used to minimize the cost function.Finally,the appropriate filter parameter is obtained according to the convergence results.In a proof-of-concept experiment,the time-domain response of two optical links with a length difference of 900 ps is successfully estimated by applying a probe signal with a bandwidth of 400 MHz.The time resolution is improved by 2.78times compared to the theoretical resolution limit of the inverse discrete Fourier transform(iDFT)algorithm.In addition,the OTD measurement error is below±0.8 ps.The proposed algorithm provides a novel way to improve the measurement resolution without applying a probe signal with a large bandwidth,avoiding measurement errors induced by the dispersion effect.
基金supported by the National Natural Science Foundation of China(Nos.61605077 and 61527820)the Jiangsu Provincial “333” Project(No.BRA2018042)
文摘Optoelectronic components and subsystems such as optically controlled phased array antennas,distributed radar networks,interferometric optical fiber hydrophones,and high-speed optoelectronic chips demand highaccuracy optical time delay measurement with large measurement range and the capability for single-end and wavelength-dependent measurement.In this paper,the recent advances in the optical time delay measurement of a fiber link with high accuracy are reviewed.The general models of the typical time delay measurement technologies are established with the operational principle analyzed.The performance of these techniques is also discussed.
基金supported in part by the National Key R&D Program of China(No.2018YFB2201803)the National Natural Science Foundation of China(No.61804159)the Natural Science Foundation of Jiangsu Province(No.BK20160802)
文摘We demonstrate microwave photonic radar with post-bandwidth synthesis, which can realize target detection with ultra-high range resolution using relatively small-bandwidth radio frequency(RF) frontends. In the proposed radar, two temporal-overlapped linear frequency-modulated(LFM) signals with the same chirp rate and different center frequencies are transmitted. By post-processing the de-chirped echoes in the receiver, a signal equivalent to that de-chirped from an LFM signal with the combined bandwidth is achieved. In a proof-ofconcept experiment, two LFM signals with bandwidths of 8.4 GHz are exploited to achieve radar detection with an equivalent bandwidth of 16 GHz, and a range resolution of 1 cm is obtained.
