间插取样光纤光栅多通道滤波器

对间插取样光纤光栅进行了理论分析和数值模拟,并依照理论分析及数值模拟的结果进行了实验研究,采用逐点扫描曝光工艺首次制作出具有10个以上通道数的光纤光栅梳状滤波器。这种方法工艺简单,控制精度要求低,是一种具有良好实用化前景的多通道光纤光栅滤波器制作技术。     

基于长周期光纤光栅的FBG解调方法北大核心CSCD

研究了基于长周期光纤光栅(long-period fiber gratings,LPFG)的光纤布拉格光栅(fiber Bragg gratings,FBG)解调方法,该方法利用LPFG的透射谱作为边沿滤波器解调FBG,其解调性能主要取决于LPFG的透射光谱深度。详细分析了CO_(2)激光写制法对透射光谱的影响,制作了透射光谱深度为25 dB的LPFG,并采用该光栅搭建了FBG解调装置,将FBG粘贴于金属应变片表面,测试了其静态与动态响应特征。实验结果表明:该方法制作简单,成本低,具有较好的线性动态范围,可以实现较高灵敏度的FBG解调。     

基于光纤叠栅的全光纤声光可调谐滤波器的特性分析

本文提出了一种基于光纤叠栅的全光纤声光可调谐滤波器, 与普通光纤布拉格光栅型全光纤声光可调谐滤波器相比, 该滤波器能够对光纤叠栅的两个中心波长进行同步调制. 理论分析了声波频率和声致应变幅度对基于光纤叠栅的全光纤声光可调谐滤波器的传输光谱的影响, 结果表明, 各阶次反射峰分别以两个主反射峰为中心呈对称关系, 且主反射峰与其所调制出的次反射峰之间的波长间隔与声波频率成正比, 而两个主反射峰所调制出的同阶次反射峰之间的波长间隔与声波频率无关; 声致应变幅度主要影响主反射峰及次反射峰的反射率的变化. 实验中, 分别测试声波频率为390 kHz和710 kHz的基于光纤叠栅的全光纤声光可调谐滤波器的传输光谱, 实验结果的变化趋势与仿真分析结果相一致.     

Spectral Talbot phenomena in sampled arbitrarily chirped Bragg gratings

We derive the general conditions for which spectral Talbot phenomena, both integer and fractional self-imaging, can be observed in sampled arbitrarily chirped fiber Bragg gratings. These results are a generalization of those previously reported in [C. Wang, J. Azaña, L.R. Chen, Opt. Lett. 29(14) (2004) 1590] in which spectral Talbot phenomena were observed in sampled linearly chirped fiber Bragg gratings. We confirm our theoretical derivations with numerical simulations.     

Simple sensing head geometry using fibre Bragg gratings for strain-temperature discrimination

In this work, a simple sensing head geometry using fibre Bragg gratings for strain and temperature discrimination is presented. The sensing head geometry consists in one fibre with two FBGs bonded with a dummy optical fibre. Due to this new configuration, different strain sensitivities of the two FBGs are obtained (≈65% difference), while temperature sensitivities remain the same. This difference in strain sensitivities is substantially larger than in all previously reported dual grating sensors. The obtained experimental errors were ±13.48 με and ±2.44 °C, respectively. It is also demonstrated that this new configuration can be used as a temperature-independent strain sensor.     

Polymer optical fibre Bragg gratings based fibre laser

For the first time the fibre laser constructed from a polymer optical fibre Bragg grating is reported. The single frequency laser with the peak power of −5 dBm and signal to noise ratio greater than 45 dB has been achieved. Further examination demonstrates the excellent characteristics of the fibre laser. First, the fibre laser can be easily tuned over 35 nm by the simple axial tension method. Second, the fibre laser has the high strain sensitivity of 1.48 pm/με with the dynamic measurement range as large as 2.37%.     

C-band continuously tunable lasers using tunable fiber Bragg gratings

We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.     

双体布拉格光栅光谱反馈特性的理论研究

基于Kogelnik理论模型,以平面波为入射光,分析了双体布拉格光栅（VBG）的反馈特性。理论分析表明,采用双VBG结构,通过控制两个VBG的中心波长差,可以使光栅反馈的效率提高,带宽加宽。对于由两块带宽100 pm、衍射效率20%的VBG组成的双VBG反馈系统,中心波长相同时,衍射效率最大（33.3%）;中心波长相差84 pm时,其带宽为单VBG带宽的1.8倍（180 pm）。由于VBG的中心波长存在温度漂移特性,因此通过改变双VBG结构中VBG的温度可以实现衍射效率和带宽的改变,为泵浦源的优化提供有效可行的方法。     

Simultaneous strain and temperature sensor based on the numerical reconstruction of polarization maintaining fiber Bragg gratings

When a short-length fiber Bragg grating is inscribed into a polarization-maintaining fiber, the resonant peaks produced by birefringence can overlap. In this case, the discrimination between strain and temperature effects is only possible by means of polarization control devices, i.e. a linear polarizer and a polarization controller. To avoid this complexity and the measurement errors that it involves, we propose a novel demodulation technique based on the numerical reconstruction of the grating physical parameters. Our technique evaluates the grating parameters from the amplitude spectrum by means of the coupled-mode equations. The convergence tool used to search the solutions is the Nelder–Mead simplex algorithm. The method is tested on uniform and apodized Bragg gratings and a very good accuracy is reported. The method is finally applied to a 2 mm-long uniform polarization-maintaining grating in order to simultaneously measure longitudinal strain and temperature.     

啁啾的引入对线性负切趾型布拉格光栅双稳特性的影响

基于耦合模理论，对线性负切趾型布拉格光栅中引入啁啾后其双稳特性的变化进行了研究.结果表明：引入正啁啾有利于改善线性负切趾型布拉格光栅的双稳态性能；通过合理选择正啁啾、线性负切趾型布拉格光栅的长度，可对其双稳态性能进行进一步优化. 关键词： 啁啾 线性负切趾布拉格光栅 双稳     

光致折变布拉格光栅实验研究

本文介绍了 2 48nm、Kr F准分子激光经过石英相位掩膜版的空间调制 ,在载氢增敏处理过的通信光纤与 B/Ge光纤上分别写入光致折变布拉格光栅的实验研究。经实验测定 ,在光栅布拉格波长上 (λH2 =15 46 .45 5 4nm ,λB/Ge=15 45 .15 5 nm) ,两种光栅反射率均大于 99% ,3d B带宽分别为 0 .12 9nm和 0 .182 nm。经比较 ,B/ Ge光纤比氢载光纤具有更好的光敏性和热稳定性     

Dynamic characteristics of nonlinear Bragg gratings in photonic crystal fibres

We study numerically the temporal and spatial dynamics of light in Bragg gratings in highly nonlinear photonic crystal fibre for a CW input signal. Our numerical model is based on the plane wave mode solver and a set of nonlinear coupled-mode equations which we solve using a variation of implicit fourth order Runge-Kutta method. We observe not only bistability of the intensity versus transmitted and reflected light but also complex dynamics. We demonstrate that for values of input intensity above the bistable region the steady state may undergo a supercritical Hopf bifurcation. For some ranges of the input intensity we also observe a coexistence of two periodic attractors. The dynamics found, in particular the features in the bifurcation diagram, strongly depend on the parameters of the fibre. Consequently, we suggest that by proper design of the photonic crystal in the cladding we can adjust such nonlinear features of the Bragg gratings as the width of the bistable region, the intensity at which the bifurcation occurs and also the characteristics of the dynamics at high values of input intensity.     

双体布拉格光栅光谱反馈特性的理论研究

基于Kogelnik理论模型,以平面波为入射光,分析了双体布拉格光栅（VBG）的反馈特性。理论分析表明,采用双VBG结构,通过控制两个VBG的中心波长差,可以使光栅反馈的效率提高,带宽加宽。对于由两块带宽100 pm、衍射效率20%的VBG组成的双VBG反馈系统,中心波长相同时,衍射效率最大（33.3%）;中心波长相差84 pm时,其带宽为单VBG带宽的1.8倍（180 pm）。由于VBG的中心波长存在温度漂移特性,因此通过改变双VBG结构中VBG的温度可以实现衍射效率和带宽的改变,为泵浦源的优化提供有效可行的方法。     

基于重构等效啁啾制作光纤光栅编解码器的光码分多址系统实现

在光码分多址(OCDMA)系统中，光纤布拉格光栅(FBG)编解码器是极具竞争力的核心器件，满足光接入网低成本、高性能的要求. 将重构等效啁啾 (REC) 技术制作的FBG作为编解码器运用于OCDMA系统. 实验采用一对511个码片、编码速率为6.4×10⁹/s的FBG编解码器，在编码匹配的情况下能恢复出输入信号，与编码非匹配的情况相比获得了8 dB的功率增益.这为REC技术制作的编解码光栅在OCDMA系统中的应用提供了实验依据. 关键词： 光纤布拉格光栅 光码分多址 重构等效啁啾 编解码器     

光纤布拉格光栅温度灵敏性的实验研究

在-150～550℃的温度范围内测量了光纤布拉格光栅中心反射波长的温度灵敏性。光栅波长的温度响应是非线性的。通过对试验数据的三次多项式进行拟合分析,结果表明:波长为1500nm左右的光栅具有相同的温度敏感性;波长对温度变化的响应(ΔλB/ΔT)主要是由折射率的变化(dn/dT)引起的,dn/dT随着温度的降低而减小;得到了温度灵敏系数关于温度的二次表达式,并给出了在-150～550℃温度范围内波长变化的快速估算。     

Effects of doping concentrations on the regeneration of Bragg gratings in hydrogen loaded optical fibers

The fabrication and optimization of regenerated Bragg gratings (RBGs) in hydrogen loaded single mode optical fibers (SMF) are presented. In addition to standard Ge-doped SMF, two kinds of B-Ge codoped SMFs with different doping concentrations are prepared using plasma-activated chemical vapor deposition (PCVD) technique to fabricate RBGs. The effects of doping concentrations on the dynamics of grating regeneration and the thermal stability of RBGs are experimentally investigated. The reflectivity of RBGs with length of 10 mm was enhanced from 20% to 40% through the optimization of doping concentrations. All fabricated RBGs can sustain in high temperature up to 1000 °C.     

取样布拉格光纤光栅的传输矩阵

根据在一般坐标系下均匀布拉格光纤光栅的传输矩阵,得到了取样布拉格光纤光栅的传输矩阵。利用傅里叶变换得到了取样布拉格光纤光栅的谐振方程。结果表明,在不考虑平均折射率变化的情况下,谐振峰的位置是由光栅的周期和取样周期共同确定的,与取样时的占空比、光栅长度和耦合系数没有关系。类似于物理光栅,取样布拉格光纤光栅也存在缺级现象,给出了出现缺级的条件。     

Numerical analysis of apodized fiber Bragg gratings formation using phase mask with variable diffraction efficiency

Scalar diffraction theory is applied to analyze the intensity distribution in the fiber core during fiber Bragg grating (FBG) fabrication using an apodized phase mask. The averaged diffraction field distribution in fiber core was calculated as a function of optical fiber position. The results show that in a case of apodized FBGs fabrication, averaged field intensity profile, and thus refractive index changes in fiber core have complex form. Moreover, it was shown that the influence of optical fiber position behind the phase mask on average intensity distribution in fiber core decreases with increasing of its diameter.     

基于亚波长二维光栅的入射角不敏感颜色滤光片研究

提出了一种基于二维亚波长光栅的具有非偏振光入射下入射角不敏感特性的反射式颜色滤光片. 采用严格耦合波分析方法详细分析了光栅周期、光栅层厚度以及固定光栅占空比下光栅的结构尺寸对反射率峰值、反射带位置及带宽的影响. 结合入射角不敏感特性, 经过优化设计得到了光栅的最终结构参数, 获得了中心波长424 nm, 峰值反射率56%, 带宽45 nm的反射滤光片.模拟结果表明, 在非偏振光入射下, 此滤光片的反射光谱表现出显著的入射角不敏感特性. 当入射角高达60°时反射带的中心波长偏移6 nm 反射率下降6%带宽增加8 nm 其参数没有较大变化通过调整光栅的结构参数可在400–520 nm范围内调节滤光片的中心波长以获得不同颜色的入射角不敏感滤光片. 关键词： 反射式滤光片 二维亚波长光栅 入射角不敏感 严格耦合波分析     

Modelling of guided-wave Bragg gratings and grating sensors using the collocation method

We have used the collocation method to model the characteristics of guided-wave Bragg gratings. The collocation method being a total field method, takes into account all modes, guided as well as radiation. We have first studied the effect of the grating structural parameters such as the grating profile and the duty cycle of periodic variation and have shown that these can have significant effect on the Bragg wavelength and the reflection spectrum. We have then obtained the response characteristics of gratings for their use in strain, temperature and pressure sensing. Our results compare very well with available experimental results. Comparisons with the coupled mode theory have also been included.