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31.
为了确保光栅单色器温度起伏引起的能量漂移不影响光束线的表观能量分辨率,建立了单色器高精度的恒温环境。结合上海光源梦之线设计,根据光栅衍射方程推导出单色器温差与能量漂移之间的关系;据此设计了沿光束方向温度起伏较小的单色器恒温环境,测试了温度控制系统不同条件下的长期温度稳定性,并通过长时间多次测量氮气K边吸收谱的方法,得到了相应的能量漂移。结果显示:温度控制系统未启动的情况下,棚屋内最大温度变化约为0.62K,测得的能量漂移约为49 meV;温度控制系统使用独立冷水机时,最大温度变化约为0.20 K,相应的能量漂移约为17meV。实验表明,建立的单色器恒温环境满足设计要求,使得单色器温差引起的能量漂移对梦之线表观能量分辨率的影响得到有效控制。 相似文献
32.
A long-period fiber grating sensor induced by electric-arc discharge has been fabricated and demonstrated for the simultaneous measurement of temperature and strain. The proposed sensor was fabricated by inscribing a sing-mode fiber with periodic electric-arc discharge technology that was produced from a commercial fusion splicer. The resonance dips formed by the coupling between cladding modes and core mode have different sensitivity responses, so the simultaneous measurement for multiple parameters was realized by monitoring the wavelength shifts of the resonance dips. Because of the easy fabrication and low cost, the sensor is promising for applications for which simultaneous measurement of temperature and strain is required. 相似文献
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将啁啾相移光纤光栅看成一多层薄膜体系,每层膜用界面传输矩阵和膜层传输矩阵表示,将每层的传输矩阵相乘后得到相移光纤光栅的传输谱.数值计算结果表明:传输谱的峰值和带宽取决于相移光纤光栅的啁啾系数、相移大小、位置及相移点的多少.该模型的精度满足设计要求. 相似文献
35.
《岩石力学与岩土工程学报(英文版)》2022,14(4):1064-1076
Hong Kong has a long history of applying masonry retaining walls to provide horizontal platforms and stabilize man-made slopes. Due to the sub-tropical climate, some masonry retaining walls are colonized by trees. Extreme weather, such as typhoons and heavy rains, may cause rupture or root failure of those trees, thus resulting in instability of the retaining walls. A monitoring and warning system for the movement of masonry retaining walls and sway of trees has been designed with the application of fiber Bragg grating (FBG) sensing technology. The monitoring system is also equipped with a solar power system and 4G data transmission devices. The key functions of the proposed monitoring system include remote sensing and data access, early warning, and real-time data visualization. The setups and working principles of the monitoring systems and related transducers are introduced. The feasibility, accuracy, serviceability and reliability of this monitoring system have been checked by in-site calibration tests and four-month monitoring. Besides, a two-level interface has been developed for data visualization. The monitoring results show that the monitored masonry retaining wall had a reversible movement up to 2.5 mm during the monitoring period. Besides, it is found that the locations of the maximum strain on trees depend on the crown spread of trees. 相似文献
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A new structure for the L-band multiwavelength switchable erbium-doped fiber laser is proposed. Overlapping laser cavities are formed by cascading fiber Bragg gratings as reflectors in a ring structure with a C-band EDFA as a common gain medium. The proposed laser is made to be wavelength-switchable by individually adjusting the loss of each overlapping cavity. Instead of using an L-band EDFA as the gain medium in the L-band fiber laser, we have experimentally demonstrated that by tailoring the gain of the C-band EDFA to have a significant gain tilt in the L-band, a lasing power efficiency of 26% can be achieved over a wide range of switchable lasing wavelengths. Following this optimal design, the side-mode suppression ratio and the minimal separation between two switchable lasing wavelengths were found to be over 42 dB and 0.33 nm, respectively. 相似文献
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A novel torsion sensor is proposed, which is composed of one long period fibre grating and one asymmetrically corrugated long period fibre grating based on the high-frequency CO2 laser pulses technology and burning fibre coating and etching cladding technology, respectively. By combing the advantages of the two aforementioned elements, a sensitivity of 331.7 and 310.3 pm/(rad/m) towards clockwise and anticlockwise direction, respectively, is reached in the experiments. 相似文献
40.
Traditional metallic gratings and novel metamaterials are two basic kinds of candidates for perfect absorption. Comparatively speaking, metallic grating is the preferred choice for the same absorption effect because it is structurally simpler and more convenient to fabricate. However, to date, most of the perfect absorption effects achieved based on metamaterials are also available using an metallic grating except the tunable dual(multi)-band perfect absorption. To fill this gap, in this paper, by adding subgrooves on the rear surface as well as inside the grating slits to a free-standing metallic grating, tunable dual-band perfect absorption is also obtained for the first time. The grooves inside the slits is to tune the frequency of the Cavity Mode(CM) resonance which enhances the transmission and suppresses the reflectance simultaneously. The grooves on the rear surface give rise to the phase resonance which not only suppresses the transmission but also reinforces the reflectance depression effect. Thus, when the phase resonance and the frequency tunable CM resonance occur together, transmission and reflection can be suppressed simultaneously, dual-band nearly perfect absorption with tunable frequencies is obtained. To our knowledge, this perfect absorption phenomenon is achieved for the first time in a designed metallic grating structure. 相似文献