环境温度宽范围变化对光纤布里渊频移的影响

搭建了光纤布里渊频移测量系统,实现了色散位移光纤20 ℃到820 ℃布里渊频移的测量,并对测量数据进行拟合. 在环境温度大范围变化时,目前采用的布里渊频移-温度一阶线性关系式对测量数据分析误差较大,针对这个问题,本文从纯石英光纤的结构特点和材料的物性系数出发,在分析光纤的热膨胀系数、光纤密度、折射率、弹性模量和泊松比与宽范围温度关系的基础上,根据布里渊频移与各物性参数的关系式理论推导了宽范围温度变化与布里渊频移之间的二次项关系式. 理论推导结果与实验数据基本符合,验证了理论分析的正确性,从而为光纤宽范围布 关键词： 光纤 高温传感 布里渊散射 布里渊频移     

布里渊散射光纤传感器的交叉敏感问题

基于布里渊散射的全分布式光纤传感器的布里渊频移同时受应变和温度的影响,无法由单一的布里渊频移解析应变或温度的信息,这种交叉敏感问题制约了传感器的实用化。介绍了目前解决交叉敏感问题的主要方法及工作原理。研究了大有效面积非零色散位移光纤(LEAF)的布里渊散射谱与应变和温度的关系,实验发现布里渊谱具有三个布里渊峰,三个峰的布里渊频移与应变和温度成线性关系,第一个峰和第三个峰的布里渊峰峰值功率的差值与温度无关,但与应变成线性关系。最后基于实验结果提出了一种解决交叉敏感问题的方案,获得了大约130με的应变测量精度和8℃的温度测量精度。     

基于微波电光调制的布里渊光时域分析传感器

针对布里渊光时域分析分布式传感原理和受激布里渊散射的特点,应用微波电光调制分布反馈式半导体激光器产生频移可调的探测光,和传感光纤中相反方向传输的脉冲激励光进行受激布里渊散射作用,当探测光和激励光的频率差在布里渊频移附近时,频移探测光和激励光产生受激布里渊散射,通过改变探测光的频移值,检测探测光功率信号,可得到沿光纤各处的布里渊频移,再利用布里渊频移和应变（或温度）的关系,计算得到沿光纤分布的传感量。设计了基于微波电光调制的布里渊光时域分析传感器实验系统,实现了25km的分布式温度传感,达到5m的空间分辨力和3℃的温度分辨力。     

基于宽带光源和自外差检测的布里渊光时域反射温度传感系统

为简化系统结构、减小相干瑞利噪声对系统性能的影响,提出了一种采用宽带光源的瑞利和布里渊散射自外差检测布里渊光时域反射温度传感系统.分析了瑞利和布里渊自外差检测原理,研究了布里渊频移和自外差信号功率与光纤温度和应变的关系.设计并搭建采用宽带光源的自外差检测布里渊光时域反射温度传感系统,获得了常温下沿光纤分布的自外差信号功率谱及不同温度时加温段光纤的功率谱,验证了布里渊频移和自外差信号相对功率变化随温度的线性增加关系.通过实验数据获得的布里渊频移和相对功率变化的温度系数分别为1.07±0.01MHz/℃和(0.37±0.09)%/℃.本文的研究结果为基于瑞利和布里渊自外差检测布里渊光时域反射传感系统的温度和应变同时测量提供了理论和实验依据.     

基于自发布里渊散射的双路分布式光纤传感器设计与实现

利用光纤中的布里渊散射光频移与温度和应变呈线性关系的原理,提出了一种基于自发布里渊散射的双支路分布式光纤传感系统。该系统利用不同种类光纤的布里渊频移差别,同时对两条线路的应力和温度进行监测,实现对被测对象多方位的同时测量,缩短了探测时间,提高了工作效率。本文实现了两路光纤的同时监测,用6 km的光纤作为传感介质,获得了4 m的空间分辨率。得到的实验结果表明,提出的系统能准确判断40 ns脉冲光在两路传感光纤沿线产生的自发布里渊背向散射光谱的中心频率变化。      

光脉冲编码对基于拉曼放大的布里渊光时域分析系统的影响

报道了光脉冲编码对基于拉曼放大的布里渊光时域分析系统(BOTDA)的影响. 实验表明,光脉冲编码能够在保证较高空间分辨率的同时减小布里渊频移的不确定性. 实验实现了49.6 km传感距离, 在整段传感光纤上温度分辨率1 ℃,空间分辨率2.5 m. 本文实验测量并分析了系统的信噪比和光功率分布特性. 关键词： 分布式光纤传感 受激拉曼散射 布里渊增益 布里渊光时域分析系统(BOTDA)     

一个新型的基于全光纤Mach-Zehnder干涉仪BOTDR系统

报道了新型的分布式传感测量布里渊光时域反射(BOTDR)系统.布里渊散射频移和强度均依赖于温度和应变,因此,BOTDR利用光纤中的自发布里渊散射作为测量信号可以实现分布式温度和应变测量.在BOTDR中,光源采用窄谱半导体激光器,并由声光调制器调制成脉冲光,经掺铒光纤放大器放大后,注入测试光纤以产生自发布里渊散射.利用双通Mach-Zehnder干涉仪分离光纤背向散射中的自发布里渊散射与瑞利散射信号,实现了自发布里渊散射的直接检测.实验结果表明基于全光纤Mach-Zehnder干涉仪BOTDR方案是可行的.     

光子晶体光纤中去极化声波导布里渊散射温度及应变响应

数值求解了光子晶体光纤中的去极化型声波导布里渊散射色散方程,研究了光子晶体光纤中的布里渊频移随泵浦波长及空气孔填充率的变化关系,以及去极化型声波导布里渊散射频移随温度、应变、声波导模式、纤芯直径及空气孔层数的关系。结果表明:布里渊频移随着波长的增大而线性减小。对于相同的波长点,增大光子晶体光纤空气孔填充率时,声波横向速度将会减小。去极化型声波导布里渊散射频移随温度及应变的增大而线性增加。同一温度条件下,高阶TR2m模式的去极化型声波导布里渊散射频移对温度的变化更为敏感;而在同一应变条件下,低阶TR2m模式的去极化型声波导布里渊散射频移对应变的变化更为敏感。去极化型声波导布里渊散射频移随纤芯直径的增加而增大,随空气孔层数的增加而减小。     

布里渊动态光栅原理及其在光纤传感中的应用

自从2007年布里渊动态光栅被首次提出用于实现光存储以来,该技术得到了国际上的广泛关注和研究.布里渊动态光栅本质上是由相干声波场激发的折射率光栅,一般情况下两束抽运光(频率差等于光纤的布里渊频移)以相同的偏振态从光纤两端注入到光纤中,通过受激布里渊散射效应激发出相干声波场,即形成布里渊动态光栅.光纤布里渊动态光栅因具有全光产生、参数灵活可控的优点,已被广泛研究应用于光纤传感、光纤特性表征、光存储、全光信号处理、微波光子学和高精度光谱分析等.本文分析布里渊动态光栅产生和探测原理,重点探讨在高性能分布式光纤传感上的应用,这些应用包括高灵敏度温度和应变分布式传感、温度和应变同时解调、分布式横向压力传感、分布式静压力(气压或液压)传感、高空间分辨率分布式传感和高精度光谱分析.     

掺杂石英系单模光纤对BSBS频移的影响

报道了对几种掺杂SiO₂石英系单模光纤的背向受激布里渊散射(BSBS)谱的实验结果,结果表明其布里渊散射斯托克斯频移主要取决于纤芯的掺杂材料和浓度,进一步分析证明了光纤掺杂后将主要通过调制杨氏模量的变化,从而导致BSBS频移量减小.     

Pockels效应对布里渊散射张量的修正

从电磁场方程和压电本构方程出发。借助于准静态近似的物理图像，导出了压电晶体中准静电场的表达式。给出了Ｐｏｃｋｅｌｓ效应对布里渊散射张量修正的一般形式．对１９种非中心对称点群晶体的高对称方向纯模作了具体计算，并对结果作了讨论．     

Ultrasonic enhanced Brillouin light scattering in water

Brillouin light spectra in water was experimentally investigated by a scanning Fabry-Perot interferometer. The optical properties of the scattering media were modulated by a plane ultrasound wave. An enhancement up to 10 times of the Brillouin signal by modulation with the ultrasound wave has been seen clearly. The dependence of the Brillouin signal amplitude on the ultrasound frequency, amplitude and the position of the ultrasound field based to the light beam was investigated experimentally. Very strong dependence of the enhancement with experimental conditions was obtained.     

Application of a phase conjugate Brillouin cavity for the generation of a train of short laser pulses

Summary An oscillator and a regenerative amplifier have been realized using a phase conjugate mirror in the amplifier laser cavity. The phase conjugate mirror, via stimulated Brillouin scattering, acts as a modulator owing to its time-depending reflectivity. A pulse-forming network applied to the amplifier increases the discharging time which contributes to get an output beam formed by a train having four short pulses. The shortest pulse was 2 ns FWHM long.     

布里渊散射及其在激光雷达中的应用

在简要介绍布里渊散射的基本性质的基础上,重点介绍了布里渊散射在激光雷达中的应用。主要分析了布里渊散射在水中声速测量、粘滞系数的测量和水中目标探测方面的原理和技术实现。     

利用不同介质进行布里渊放大的研究

研究了受激布里渊散射振_放双池系统中振荡池和放大池选用不同种类介质的情况.理论分析 结果表明，当两种介质的布里渊频移接近，布里渊线宽有交叉时，系统仍具有放大作用.采 用CCl4作为放大池介质，CCl4/CS2的混合介质作为振荡池介质，利用Nd:YAG调Q 激光研究了布里渊频移的偏离对布里渊放大的影响，结果表明，当布里渊频移的偏离较小时 ，其种子光放大率和种子光脉宽压缩率仍然很大.采用CS2作为放大池介质，苯作为振荡池 介质，对振 放双池系统进行了实验研究，其种子光放大率达到44，种子光脉宽压缩率为 72，相位共轭保真度为98%，种子光放大率的稳定度小于3%. 关键词： 受激布里渊散射 布里渊放大 布里渊频移 布里渊线宽     

Dynamical properties of water-methanol solutions: Brillouin and depolarized Rayleigh scattering

Summary We have performed Brillouin and depolarized Rayleigh light scattering on water-methanol solutions as a function of methanol molar fraction and temperature. For this system, molecular-dynamics (MD) simulation predicts that a shell of water forms around a methanol molecule, prediction which has been recently confirmed by neutron diffraction experiments. The results obtained by light scattering and presented here confirm previous observations and show, in addition, an increase of the stability in time of the water structure in the shells when temperature decreases and methanol concentration approaches a particular value. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Nature of depolarized quasi-elastic light scattering in associated and non-associated liquids

Summary An analysis of Rayleigh-wing spectra on two isomers of propanol (C₃H₇OH) and on two of their Br-based isomorphous systems (C₃H₇Br) is presented. The performed measurements, over a wide temperature range, allow us to identify two different processes characterizing the response of both the alcohols. A comparison between the rotational dynamics of the linear normal-propanol (1-propanol) and the more sterically hindered iso-propanol (2-propanol) is performed. At the same time, the role played by the H-bond in the associative properties of hydrogenous systems is investigated by comparing the dynamical response of the two alcohols with that of 1-bromopropane and 2-bromopropane, in which the O−H ?active? sites are replaced by ?inert? bromine atoms. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Sound propagation and viscosity in water short-chain amphiphiles solutions,evidence of percolation phenomena

Summary A water/butoxyethanol solution has been investigated by means of several techniques (viscosity, ultrasound and hypersound) as a function of concentration and temperature. The butoxyethanol molar fraction range investigated was situated between 0.015 and 0.09, while temperature ranged between −10°C and +45°C. We observed the building-up of large structures lowering the temperature, in particular below +15°C. All data coming from different techniques seem to confirm such a picture and indicate that this aggregation phenomenon is a percolation-like process. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Small-angle light scattering in dense microemulsions,transition from droplet to bicontinuous phase

Summary We have performed extensive small-angle light scattering (SALS) measurements on a three-component microemulsion (AOT/decane/water) as a function of the dispersed phase concentration and the temperature. All samples have a water/AOT molar fractionw=40.8. Such a system presents a very complex phase diagram with many structural configurations. With the SALS technique, we have been able to observe all the phase separation lines. In particular we give details on the system structure on the percolation phenomenon and on the bicontinuous phase recently observed. In particular we show that the percolation is driven by a long-scale aggregation between microemulsion droplets. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Inherent spectral distortions in pump-probe Brillouin scattering spectroscopy

It is shown that the pump-probe technique in Brillouin scattering spectroscopy is accompanied by two specific distortions to a registered spectrum. The first appears due to an acoustic wave that unavoidably accompanies in a continuous medium the density wave driven by the pump and probe signals. The registered spectrum then splits to two spectral components, one corresponding to the propagation velocity of the driven density wave, and the other to the acoustic velocity. The other distortion is asymmetry of the spectrum which is shown to occur when the velocity of the driven density wave is greater than the acoustic velocity in the medium.