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长周期光纤光栅(long-period fiber grating,LPFG)是一种宽带的透射型无源光子器件,在光纤通信和光纤传感领域应用广泛.本文从折射率空间调制的角度,根据栅格周期长短、折射率调制深度和栅面法线取向三个特征参数,对LPFG进行了分类并分析了其不足,定义了新型长周期光纤光栅(novel long-period fiber grating,NLPFG)概念并指出了其研究意义;阐述了典型的LPFG写制新技术,建立了NLPFG模型和设计理论;提出了NLPFG正、反向设计流程,阐述了NLPFG典型设计方法;综述了近年来NLPFG的研制及典型应用,展望了NLPFG研究的发展趋势. 相似文献
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不同包层直径的倾斜光纤光栅折射率传感特性 总被引:3,自引:0,他引:3
倾斜光纤光栅的透射谱中有纤芯模和大量的包层模,它们具有与布拉格光栅相同的温度特性.利用HF酸腐蚀的方法得到具有不同包层直径的倾斜光纤光栅,研究了其对外界折射率的传感特性.结果表明,外界环境折射率在1.333~1.4532之间变化时,同一直径倾斜光纤光栅的高阶包层模的敏感性要比低阶包层模强;随着包层直径的减小,包层模的敏感性增强,且在折射率比较高的环境中有更高的敏感性.因此,利用倾斜光纤光栅的温度特性不仅可以解决温度交叉敏感问题,而且通过小同的腐蚀程度能定制所需要的灵敏度,以实现对环境折射率的高灵敏度测量.该办法可应用于对生物和化学等高灵敏度传感领域的各种溶液进行实时监控. 相似文献
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A novel fiber grating pair that consists of a conventional long-period fiber grating and a fiber Bragg cladding grating (FBCG) is proposed. The FBCG is a new type of fiber grating in which refractive index modulation is formed in the cladding. Through the coupled-mode theory, we accurately calculate the coupling coefficients between modes supported in the fibers. And some other mode coupling features in the fiber cladding gratings are analyzed in detail. The calculation of the modes involved in this paper is based on a model of three-layer step-index fiber geometry. Then, we have investigated the sensitivity characteristics for variation of the modulation strengths of the fiber Bragg cladding gratings’ resonance peaks and the long-period cladding gratings’ (LPCGs) dual resonant peaks. Finally, the modulation strength sensitivity of the grating pair’s three resonant peaks is demonstrated, and the results indicate that these grating pairs may find potential applications in optical fiber sensing. 相似文献
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The spectrum of a Bragg grating in a multimode optical fiber can be controlled by the number of irradiation pulses during the writing procedure. Hence, a single mode grating can be fabrication readily within a multimode fiber. The width of the stop band of the grating can also be controlled by means of the number of irradiation pulses. A tilted grating leads to the coupling of core mode to cladding mode, and when the tilt is sufficiently large, eventually to radiation mode. In the case of small tilt, the grating spectrum is the sum of the core-core mode spectrum and the core-cladding mode spectrum. 相似文献
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模式耦合理论在圆周对称长周期光纤光栅建模中的应用 总被引:4,自引:0,他引:4
长周期光纤光栅是不同于光纤Bragg光栅的一种光纤光栅器件 ,根据模式耦合理论 ,长周期光纤光栅表现为前向传播的纤芯导模和同向的各阶次包层模式之间的耦合。分析研究了长周期光纤光栅轴向的模场变化。忽略轴向的模式耦合以及包层模式之间的相互耦合作用 ,并认为折射率指数的调制只存在于纤芯中 ,建立了简化的长周期光纤光栅数学模型。对圆周对称轴向均匀型长周期光纤光栅谱特性进行了仿真 ,其结果与实验结果基本吻合 ,表明了简化的数学模型的合理性 相似文献
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啁啾叠栅光纤光栅反射特性和时延特性的研究 总被引:1,自引:0,他引:1
从耦合模理论出发,用矩阵分析法分析由两线性啁啾光纤光栅构成的啁啾叠栅光栅的反射特性和时延特性,分别得到光栅长度、啁啾系数和折射率变化峰值对反射谱及光栅时延的影响. 相似文献
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提出了一种光纤横截面折射率变化呈旋转非对称变化的长周期光纤光栅(R-LPFG) 结构,并利用多层圆波导理论和横截面折射率离散分析方法,结合模式耦合方程组和数值求解方法理论分析了这种光栅的模式耦合特征.理论分析表明R-LPFG纤芯基模主要与一阶非对称包层模发生耦合,当光栅旋转度逐渐变大时,R-LPFG基模会与一阶非对称包层模的奇模和偶模同时发生耦合,这就会使原来单一的谐振峰逐渐分裂成双峰,这是常规光栅类型所不具有的透射谱特征.由于R-LPFG的双峰来自同一对耦合模式,它们对温度的响应很相似,因此可利用双峰间
关键词:
光纤传感
光纤光栅
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旋转折变 相似文献
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De-Long Zhang Yun Zhang Yu-Ming Cui Cai-He Chen E.Y.B. Pun 《Optics & Laser Technology》2007,39(6):1204-1213
A comprehensive, complete theory suitable for a long period grating (LPG) on/in a planar or channel waveguide is described on the basis of coupled mode theory. The theory aims at key characteristic parameters with respect to the effect of the LPG, including resonance wavelength, transmission power of the guided mode in the waveguide, full-width at half-maximum (FWHM) of the power attenuation band in transmission spectrum of the guided mode, and coupling coefficient between a guided and a coupled mode. The type of the grating including relief and index modulation, different polarization state combinations of the guided mode and the resonant mode, and slanted grating structure are considered in this theory. The influences of the coupling between two guided modes and between a guided mode and a substrate mode are discussed. The role of cladding layer in a long period waveguide grating is demonstrated in particular. Finally, the expressions for the sensitivity of resonance wavelength as a function of external temperature, pressure and surrounding refractive index are derived. 相似文献
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Ou Xu Shaohua Lu Yan Liu Bin Li Xiaowei Dong Li Pei Shuisheng Jian 《Optics Communications》2008,281(15-16):3990-3995
On the basis of the coupled-mode theory, a detailed investigation of the optical spectral characteristics is presented for uniform tilted fiber gratings. Explicit expressions are derived for the spectral parameters of reflection and transmission spectra. Numerical simulations are carried on to show the dependences of grating spectral responses on the structural parameters, such as tilt angle, grating length, index modulation amplitude and polarization states. The effects of these parameters on shaping the grating spectra are discussed comprehensively. The physical mechanism and intuitive phase-matching vector model are provided to explain the unique behaviors of transmission loss spectra. The results are helpful for providing a better understanding of the spectral behavior of the tilted fiber grating. 相似文献
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根据倾斜光纤光栅(TFBG)和表面镀金的TFBG传感器测量折射率的基本原理,通过OptiGrating软件模拟了不同浓度溶液下TFBG的透射谱和芯层模与某阶包层模耦合引起的谐振峰,初步得出了TFBG各阶包层模随着外界折射率的增大而向右偏移、在一定的传感范围内中心波长与外界折射率呈线性关系的结论。用小型离子溅射仪对TFBG镀45 nm厚度左右的金膜,并用扫描电镜在微观上观察镀膜效果。通过不同浓度下的NaCl溶液、MgCl2溶液、CaCl2溶液实验,对比研究了裸TFBG和镀金TFBG传感器对溶液折射率的传感特性。从而验证了模拟仿真得出的结论并定量分析得知:镀金后具有表面等离子体共振的TFBG溶液折射率灵敏度大于500 nm·RIU-1,而裸TFBG为2 nm·RIU-1左右,大约提高了200~300倍,且在一定范围内中心波长与溶液折射率的线性拟合度都在0.99以上。 相似文献
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Plasmon resonances in gold-coated tilted fiber Bragg gratings 总被引:1,自引:0,他引:1
The transmission spectrum of fiber Bragg gratings with gratings planes tilted at a small angle (2 degrees -10 degrees) relative to the fiber axis shows a large number of narrowband cladding mode resonances within a 100 nm wide spectrum. When a gold coating with a thickness between 10 and 30 nm is deposited on the fiber, the transmission spectrum shows anomalous features for values of the outside medium refractive index between 1.4211 and 1.4499. These features are shown to correspond to the excitation of surface plasmon resonances at the external surface of the gold film. 相似文献
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基于包层模的光纤布拉格光栅折射率传感特性 总被引:5,自引:0,他引:5
提出了基于光纤布拉格光栅(FBG)包层模式的折射率传感方案。实验中,利用不同浓度的丙三醇水溶液作为外界折射率传感溶液,采用氢氟酸溶液化学腐蚀的方法来减小光纤包层的直径以增大包层模式对外界折射率的敏感度,研究了腐蚀后光纤布拉格光栅包层模式的耦合波长对外部折射率的变化关系。实验结果表明在1.3300~1.4584的折射率范围内,包层模式耦合波长随外界折射率增大而增大,在接近光纤包层折射率处具有很高的折射率灵敏度,最大达到了172 nm/riu(refractive index unit)。而且,包层模谐振的光谱半峰全宽(约0.07 nm)仅为布拉格纤芯模谐振光谱半峰全宽的1/4,能够获得更好的传感精度。 相似文献
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振幅掩膜紫外写入的长周期光纤光栅特性研究 总被引:6,自引:2,他引:4
振幅掩膜紫外写入的长周期光纤光栅的纤芯折射率分布函数为矩形波。以三层阶跃折射率光波导结构基础,用弱导标量近似和标量耦合模理论分析折射率调制类型为矩形波的长周期光纤光栅的特性。详细地给出耦合模方程近似处理的方法,并说明了其合理性。用数学软件Matlab进行了数值模拟计算,发现折射率调制类为矩形波的光栅传输谱不是由它的各次余弦光栅谱的线性叠加而成的。还研究了外部环境折射率、包层半径、栅占空比等光栅结构参量对矩形折射率调制的光栅传输谱的影响。同时指出了每阶包层模的双谐振峰位置随栅参量的变化规律。刊■刊『_型,刿j1 相似文献
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少模光纤布拉格光栅折射率传感的分析与测量 总被引:7,自引:3,他引:4
理论分析和模拟计算了少模光纤布拉格光栅基模及高阶模的耦合与传输特性,得到在相同外部折射率变化情况下,少模光纤基模与高阶模耦合对应的布拉格波长变化,比正、反向基模之间耦合对应的布拉格波长变化显著增大.实验上制作了少模光纤布拉格光栅,测量了基模之间以及基模与高阶模之间对应的布拉格波长随外部折射率、温度变化的情况,得到与理论分析相符的结果.而对于温度变化对折射率测量结果干扰的问题,提出了通过计算布拉格波长差来克服温度影响的方法.这些结果为采用布拉格光纤光栅测量外部折射率变化提供了一种新的途径. 相似文献
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对重构多信道光纤光栅的离散层析算法进行了优化.在各信道加入相移的基础上,运用非线性最小二乘法对耦合系数进行高斯曲线拟合,降低了折射率调制深度的最大值且可以将剧烈变化的折射率调制深度平滑化.仿真表明,较之改进前的折射率调制最大值(0.001 3),利用新算法在折射率调制最大值为0.000 5时成功设计了一个8信道光纤光栅,极大地降低了对光纤光敏性的要求.同时,折射率调制曲线的平滑化降低了光栅的实际刻写难度. 相似文献