光纤光栅传感器信号解调方法综述

当光纤光栅传感器上的温度或应力发生变化时,布拉格反射波长也随之发生漂移,根据这个漂移量便可判断待测量大小,因此,人们提出了许多解调方法.文章论述了几种常用的光纤光栅传感器信号解调方法,分类评述了这几种方法的工作原理和性能,分别给出了其典型的实验原理图,并对其优点和缺点进行了分析比较.     

All-fiber Based Er^3＋∶Yb^3＋ Co-doped Fiber Laser

An all-fiber based Er^3＋ ：Yb^3＋ co-doped double clad fiber laser operating at 1 550 nm is demonstrated. By using 9 m long Er^3＋ ： Yb^3＋ co-doped fiber（EYDF） as the gain medium, and using a pair of fiber Bragg gratings as wavelength filters, the line-width of the output laser is as narrow as 0.2 nm and the output power is more than 6 mW. The fluorescent effect of the laser before its emission is also studied. And it is found that the Er^3＋ ： Yb^3＋ co-doped double-clad fiber laser also exhibits a high gain for Yb^3＋ transition near 1 080 nm.     

改进模拟退火算法在FBG传感网络中的应用

通过分析传统模拟退火（Simulated Annealing）算法的原理和存在的不足,提出了一种改进的模拟退火算法.改进的算法增加了记忆当前最好状态的功能以避免遗失当前最优解,并设置双阈值使得在尽量保持最优性的前提下减少计算量.根据光纤光栅传感网络谱形状复用技术和模拟退火算法的特征,设计了高效的计算能量增量的方法,加快了算法的运行速度.仿真和实验结果表明,改进的算法比传统的模拟退火算法在解决光谱形状复用技术问题上具有更快的收敛速度,解的质量也有很大程度的提高.     

基于边缘滤波的FBG解调系统

实现了一种基于边缘滤波的FBG解调系统,系统采用宽带光源、隔离器、分束器、FBG、耦合器及边缘滤波器等光学元件,来采集变化的光信号,同时设计光电探测器进行光电信号转换及放大滤波处理,并采用NI USB-6361进行数据采集,将模拟信号转换为数字信号,最后采用Labview进行处理,最终得出所要测量值。     

Fiber Bragg Gratings in Small-Core Ge-Doped Photonic Crystal Fibers

This paper reports fiber Bragg gratings （FBGs） inscribed in a small-core Ge-doped photonic crystal fibers with a UV laser and a Talbot interferometer. The responses of such FBGs to temper- ature, strain, bending, and transverse-loading were systematically investigated. The Bragg wavelength of the FBGs shifts toward longer wavelengths with increasing temperature, tensile strain, and transverse-loading. The bending and transverse- loading properties of the FBGs are sensitive to the fiber orientations.     

Transmission properties of the single mode fiber with a cross-sectional micro-channel investigated using time-domain finite difference (FDTD) method

Light scattering by a micro-channel intersecting core of a single mode fiber (SMF) has been investigated by use of two dimensional time-domain finite difference (2D-FDTD) method and the numerical results are in good agreement with those reported in the experiments. The transmission properties of the SMF with such a micro-channel can be attributed to the combined results of scattering effect and FP resonance effect. It is suggested that the SMF with micro-channel of about 4–6 μm in diameter can be effectively used for refractive index sensing with a high refractive index resolution up to ∼10⁻⁵.     

高强度电磁脉冲对光纤的影响及防护措施

光缆在高强度电磁脉冲的作用下,会引起光纤传输特性的变化,导致模间色散的增加和信号的失真。主要论述了光缆在高强度电磁脉冲影响下的非线性效应,并提出了有效的防护措施。     

熔融拉锥技术在光纤耦合传输中的应用

为了实现光纤激光器和放大器系统中不同参量光纤的低损耦合,采用光纤拉锥方法来实现光纤连接。经过理论分析,在大数值孔径光纤传输到小数值孔径光纤时,采用光纤拉锥技术可以有效地提高传输功率。采用改造的大模光纤熔接机进行拉锥实验研究,精确控制拉锥时间、放电功率、步进量和步进速率可以获得不同的拉锥形状。采用光纤拉锥元件对标准单模光纤和大模场光纤进行耦合实验,得到纤芯内传输的耦合输出效率由之前的50%提高到85%,获得了低损连接效果。结果表明,熔融拉锥技术为不同光纤之间的耦合提供了一种简单实用的方式。     

Metal coating of fiber Bragg grating and the temperature sensing character after metallization

In this study, the fiber Bragg grating (FBG) was metallized with a nickel coat using an electroless-electro plating method. Under the optimum conditions, the surface of chemical plating and electroplating coat are smooth and compact, there is not any visible defect in the cross-section. The effects of the nickel coat on the properties of the fiber sensor were studied. With this plating method, the FBG can be well protected and its sensing properties can be changed. When the temperature is changed, a thermal stress between the metal coat and the fiber will be induced because of the thermal expansion coefficients difference. The thermal stress influence on the temperature sensing properties of the metalized FBG was analyzed, and a physical-mathematical model for FBG temperature sensing was presented. Experimental results show the mathematical model is feasible to explain the mechanism of temperature sensitivity enhancement for metalized FBG.     

椭圆芯保偏光纤模间干涉的研究

对椭圆芯保偏光纤的模间干涉现象进行了仿真研究,得到了其干涉输出光强分布同模间相位差之间的关系.将一种椭圆芯保偏光纤进行等面积矩形变换后,通过马卡梯里近似方法对两个低阶模式LP01模和LPeven11模的传输特性及传播常数进行了数值计算,得到了归一化传播常数和归一化截止频率之间的关系.通过实验得到了两个模式之间干涉模斑远场图样,表明椭圆芯保偏光纤的模间干涉特性可以应用于应力、电压等的测量.模间干涉将传感臂和参考臂集于一根光纤中,具有很好的抗环境干扰能力.