基于光纤光栅的输油管道安全监测系统

针对穿插于滑坡体内的输油管道,提出一种基于光纤光栅传感的管道安全监测系统。系统由光开关和光纤光栅解调仪共同完成数据的自动测量和存储,并利用GPRS方式进行数据传输。利用已知管道上三点应力求最大应力的方法,选用自行研制的光纤光栅传感器监测管体应力。该传感器除了具有抗电磁干扰、耐腐蚀、稳定性好的优点,还可以实现温度补偿,不但排除了温度对测量结果的影响,还可以测量环境温度。经实际应用证明：该监测系统可实现实时监测,性能稳定。     

A high sensitive fiber Bragg grating cryogenic temperature sensor

At cryogenic temperature, a fiber Bragg grating （FBG） temperature sensor with controllable sensitivity and variable measurement range is demonstrated by using bimetal configuration. In experiments, sensitivities of -51.2, -86.4, and -520 pm/K are achieved by varying the lengths of the metals. Measurement ranges of 293 - 290.5, 283 - 280.5, and 259 - 256.5 K are achieved by shortening the distance of the gap among the metals.     

长周期光纤光栅折射率特性仿真的新方法

基于长周期光纤光栅的模式耦合机理,提出一种快速模拟长周期光纤光栅折射率特性的方法。该方法在计算包层模式的有效折射率时分开计算,在环境折射率小于包层折射率时采用二分法和分步搜索法结合计算包层模式的有效折射率,在环境折射率大于包层折射率时采用Nelder-Mead加分步搜索法求解包层模式的有效折射率。在应用谐振波长的决定式求解与环境折射率的匹配的谐振波长时,采用变区间应用二分法求解而不是传统的逐步搜索法求解谐振波长。数值结果与实验结果做了对比,两者基本一致。实践证明,该方法方便快捷,比一般的方法速度提高7倍以上。     

射频光纤链路γ射线辐致损伤特性实验研究

由于空间环境中宇宙辐射无处不在,工作在空间环境的光纤系统必须考虑辐致损伤特性。建立了10GHz的射频光纤链路传输系统,分别采用单模光纤和保偏光纤作为传输媒质。利用60 Co`γ射线源,在剂量率1rad/s总剂量50krad下,对射频光纤链路进行辐照实验,对两种系统做对比分析。实验结果表明,单模光纤链路的辐致损耗绝对值较大,保偏光纤链路的辐致损耗绝对值较小;单模光纤的幂律模型指数较保偏光纤大,即同样的辐照剂量,单模光纤受影响程度大。在辐照起主要影响因素的阶段,单模光纤延时差受辐照影响程度较保偏光纤稍小。辐致损耗和辐致延时差对光纤长度都有线性累加作用。从整体水平看,50krad的辐射总剂量对两种光纤造成的损伤并不大,传输的信号仍在可用的范围之内。     

Temperature-insensitive Mach-Zehnder interferometric strain sensor based on concatenating two waist-enlarged fiber tapers

A novel temperature-insensitive strain sensor,based on an in-line Mach-Zehnder interferometer,is fabricated by concatenating two waist-enlarged fiber tapers separated by a short piece of photonic crystal fiber. The interference spectrum of the proposed sensor is analyzed in detail.Experimental results demonstrate that this sensor has a strain sensitivity of.3.02 pm/μεand maintains the temperature insensitivity feature. The proposed sensor has great potential in diverse sensing applications due to its advantages,such as its compact size,low cost,and simple fabrication process.     

Experimental investigation on a software synchronous optical sampling technique based on periodically poled lithium niobate

A software synchronous optical sampling system is constructed based on sum frequency generation (SFG) in periodically poled lithium niobate (PPLN). Five gigahertz of a non-return-to-zero (NRZ) data signal is sampled by sampling pulse with the repetition frequency of 29.31 MHz. The power of the SFG light is set at 23 dBm, and an eye diagram is successfully recovered. A band-pass filter is added before the sampling pulse is subjected to erbium-doped fiber amplifier to reduce gain competition and ensure a high power level of SFG.     

Sensitivity enhancement of distributed polarization coupling detection in Hi-Bi fibers

The intensity and position of the coupling points in high birefringence(Hi-Bi)fibers can be detected effectively using distributed polarization coupling(DPC)detection.The detection sensitivity can decrease due to mechanical vibration disturbance and environment noise.Thus,a method based on empirical mode decomposition is proposed to detect weak mode coupling points.The simulation and experimental results illustrate that the proposed method can suppress the noise effectively and improve sensitivity significantly.The method can identify coupling points as weak as-60 dB embedded in noise automatically and effectively.The algorithm is applicable for DPC,and the experimental sensitivity is improved by 10 dB.     

新型闪烁材料——闪烁光纤

本文简要地介绍闪烁光纤的工作原理,指出了掺Tb~(3+)和Ce~(3+)闪烁玻璃光纤的谱特性和衰变时间常数,将它们和CeF_3与其它元机闪烁材料的特性进行了比较,从而得知CeF_3及掺Ce~(3+)闪烁玻璃光纤存在着潜在的巨大应用市场。 The working principle of scintillating fibers is briefly introduced in this paper. Thedecay time constant and spectral properties of the scintillating fibers of Tb_2O_3 and Ce_2O_3 glass aregiven. Comparing the properties of materials above and CeF_3 with those of other inorganic scintillatingmaterials, we find that CeF_3 and scintillating fibers of the Ce_2O_3 have an immense potential applicationmarket.     

空间扫描型光纤法布里珀罗传感解调系统中CCD的光照度数学模型研究

针对空间扫描型光纤法布里珀罗（F-P）传感解调系统中CCD的光照度分布建立了数学模型,研究了不同帧扫描频率下CCD输出信号和信噪比。利用已设计的解调模块进行了CCD光照度分布的实验,实验结果表明,当帧扫描频率不同时,CCD各个像素输出信号电压的实验值与计算值的相对误差均小于2.5%,同一像素输出信号电压的实验值与计算值的相对误差变化数值均小于0.005,随实验所用CCD帧扫描频率变化,信噪比以184 Hz为分界点以两种变化斜率改变,验证了数学分析模型的有效性。     

磁绝缘传输线阻抗变化对空间电子流的影响

介绍了磁绝缘传输线的阻抗大小、传输电压及电流大小对其产生的空间电子流大小及阴极电子鞘层厚度的影响。运用CHIPIC软件建立四层圆盘锥形磁绝缘传输线A层的近似化三维模型进行模拟,对比理论计算值与模拟值,并与相关文献的二维模拟结果进行对照,验证三维模拟的正确性。最后,模拟研究了圆盘锥形磁绝缘传输线阴阳极之间的间距变化对传输效率的影响。