共查询到20条相似文献,搜索用时 31 毫秒
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级联长周期光纤光栅和Bragg光纤光栅的光学特性 总被引:1,自引:0,他引:1
基于耦合模理论及传输矩阵法,给出了级联长周期光纤光栅和Bragg光纤光栅系统(CLBG)的耦合模方程与总传输矩阵,理论模拟了CLBG的反射谱,得到的反射峰位置与已知文献中所给出的两个反射峰的位置关系相吻合。在此基础上,模拟了镀膜CLBG之间的光纤长度、薄膜折射率、薄膜厚度等参数对反射谱的影响。由仿真结果可知,CLBG反射峰中受长周期光纤光栅和Bragg光纤光栅共同影响产生的反射峰对外界环境的变化非常敏感,其对薄膜折射率的分辨率较单个镀膜长周期光纤光栅高2个数量级,表明CLBG在薄膜传感领域具有重要的应用价值。 相似文献
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《Optical Fiber Technology》2007,13(1):32-38
A novel and efficient approach is proposed to calculate transmission and reflection spectra of propagating core mode and higher-order cladding modes when the fiber Bragg gratings (FBGs) are modulated by acoustically induced microbending. Based on a matrix form of first-order differential equations and its eigen-values/vectors using similarity transformation method, coupled-mode equations modeling acoustically induced microbending in FBG with a thin cladding can be transformed into a simple mathematical formulation. This method would be straightforward and thus beneficial to solve directly multimode coupled equations in comparison with a previous used fundamental matrix method and a Runge–Kutta algorithm. This simple model provides us a good view of co-directional and contra-directional couplings caused by acoustically induced microbending through FBGs. 相似文献
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Bragg gratings in multimode and few-mode optical fibers 总被引:7,自引:0,他引:7
Bragg gratings in optical fibers in multimode propagation are investigated experimentally and theoretically. Bragg gratings formed in optical fibers in multimode propagation show multiple reflection peaks or multiple transmission dips in the reflection or transmission spectra, respectively. For standard graded-index multimode fiber, the number of reflection peaks of a Bragg grating depends on excitation condition of propagating modes. The number of reflection peaks of a Bragg grating at around 1.55 μm is 19 for highly multimode excitation and 3-4 for lower order mode excitation. We analyze the phase-matching conditions of the propagating modes and identify half of the reflection peaks as the reflection to the same mode and the rest as the reflection to the neighboring modes. In dispersion-shifted fiber, a Bragg grating at around 0.8 μm in three-mode propagation shows three reflection peaks in the reflection spectrum. The temperature dependence of each reflection peak is similar to that of a conventional Bragg grating in single-mode fiber. Polarization dependence measured on a Bragg grating in multimode graded-index fiber is negligible. An advantage of Bragg gratings in multimode fiber (MMF) and the applications are discussed 相似文献
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Muller M.S. Hoffmann L. Sandmair A. Koch A.W. 《Quantum Electronics, IEEE Journal of》2009,45(5):547-553
Embedded fiber Bragg gratings can be subjected to arbitrary states of strain including shear strain. Such perturbations can cause coupling between polarization modes. Coupled-mode theory in Bragg gratings so far neglected this effect and only considered forward-backward coupling. Polarization mode coupling within a Bragg grating leads to interdependencies between Bragg reflection peaks which have so far been unaddressed. We formulate a full strain tensor treatment of fiber Bragg gratings, considering the coupling of the polarization modes within the grating. We give an approximation for the coupling coefficients affecting the polarization mode coupling and numerically solve the coupled-mode equations for representative states of strain. We show in which way shear strain affects the optical response of a grating and demonstrate how the fiber's beat length influences this characteristic. 相似文献
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Muller M.S. Buck T.C. El-Khozondar H.J. Koch A.W. 《Lightwave Technology, Journal of》2009,27(23):5223-5229
Fiber Bragg grating (FBG) sensors have become commercially available sensors for the measurement of temperature, strain, and many other quantities. One interesting application is the embedding of these sensors, during which shear strains can arise inside the sensor. As we have recently demonstrated by a full-tensor coupled-mode analysis, shear strains do influence the spectral response of fiber Bragg sensors, and thus have to be considered. In this paper, we use the theory behind this analysis to compute the direct influence of shear strains on the output of a FBG measurement system, and show cases where shear strain effects are relevant. Furthermore, we compare the sensitivity of different interrogation algorithms toward shear strain influences on the measurement system output. To model the experimentally relevant unpolarized light sources, we derive a model using the monochromatic waves of coupled-mode theory. We apply the unpolarized light to the FBG shear strain problem and show that for unpolarized light, shear strain has to be taken into account as well. We find absolute measurement errors in the range of 100 pm. For typical normal strain measurements, this would be of an order of 10% of relative error. 相似文献
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A method to interrogate fiber Bragg grating vibration sensor by narrow line width light is demonstrated. The interrogation scheme takes advantage of the intensity modulation of narrow spectral bandwidth light, such as distributed feedback laser, when a reflection or transmission spectrum curve of an fiber Bragg grating (FBG) moves due to the strain which is applied on the sensor. The sensor's response to accelerating frequency and amplitude is measured by experiment. The factors which have impacts on the sensitivity of the interrogation system are also discussed. 相似文献
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Fiber Bragg gratings (FBGs) with random fluctuations are investigated theoretically by using the coupled-mode theory. The fluctuation of the period causes interference inside the grating, which makes some light with wavelength inside the reflection bandwidth transmit through the grating and thus split the reflection spectrum. Simulation results show that low-frequency disturbed random fluctuation easily forms interference because the coupling wavelength in different position of the grating is different, while small high-frequency disturbed random fluctuation has almost no influence on the reflection spectrum and large high-frequency disturbed random fluctuation makes the grating incontinuous, which results in the interference. At the same time, a numerical method based on the fourth-order Runge–Kutta formula is developed to solve the coupled equations directly. By using this method, a grating with complex index modulation does not need to be treated as a superposition of a set of uniform grating with sinusoidal index modulation through the Fourier transform. 相似文献
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《Optical Fiber Technology》2000,6(3):299-323
This paper reports the birefringence effects on fiber Bragg grating (FBG) in sensors, optical communications systems, and devices. We have studied and analyzed the optical and mechanical property changes of FBG when the grating zone is subjected to a static transverse load in the case of plane strain and stress. The results presented for plane strain confirm the calculations established in previous research work. We extended these calculations for plane stress and used coupled-mode theory to deduce the reflection spectra of the disturbed FBG. Results were in good agreement with previous published results for plane strain. The simulated results show that the Bragg reflection wavelength changes for the x-polarization and the y-polarization are much more significant for plane stress than for plane strain. Moreover, the Bragg reflection wavelength variation is much more important for x-polarization than for y-polarization for both plane strain and plane stress. This research holds implications for the improved integration of these devices into smart structures and materials as well as optical communications systems and devices. 相似文献
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利用模式理论和传输矩阵法,对基于包层空气孔排布为正八边形对称结构的光子晶体光纤光栅(PCFG)的模式截止特性以及谐振特性进行了研究,得出了此种光子晶体光纤光栅的模式截止条件和可传导的模式,并利用得到的模式截止条件,提出利用相位匹配条件设计相应的光纤光栅周期来得到满足需要的谐振波长,同时给出了谐振峰的反射谱图。研究表明,通过合理选择此种光子晶体光纤光栅的结构参数,可以实现需要的单模传输以及定制波长处的主谐振峰的谐振。所研究的基于包层空气孔排布为正八边形对称结构的锗掺杂光子晶体光纤光栅有望更好地应用于光子晶体光纤光栅传感领域。 相似文献
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《Optical Fiber Technology》1999,5(2):145-164
Using an accurate optical system simulation for Bragg fiber grating dispersion compensators, the fundamental limitations on system performance incurred by these devices operating in reflection and transmission, are studied. When the devices are operating in reflection, the limitation on system performance is due to group delay and reflectivity ripple. When they are operating in transmission, the limitation on system performance is due to dispersion slope of the grating. A range of issues, including the impact on system performance of ripple period and amplitude, concatenating many gratings, and system bit rate are considered. The results show that systems based on WDM with lower channel line rates are the more resilient to limitations introduced by these devices than high-speed TDM systems. 相似文献
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多波长啁啾光纤光栅叠栅的数值分析和设计 总被引:2,自引:2,他引:0
为了研究多波长啁啾光纤光栅叠栅的反射和时延特性,提出多波长啁啾光纤光栅叠栅的耦合模理论方法,得到波长间隔Δλ=1.6nm的4波长和8波长的啁啾叠栅的反射谱和时延特性的数值分析结果,并设计了波长间隔Δλ=0.4nm的8波长的啁啾叠栅,数值分析结果与实验结果非常一致.结果表明,多波长啁啾光纤光栅叠栅的耦合模理论是可靠的,可用来分析其各种特性,此方法对多波长啁啾叠栅的设计和制作具有重要的参考价值. 相似文献
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Standard Bragg filters (dielectric waveguides with a grating overlay) show a stopband only in reflection. Filters with quarter-wave-shifted gratings have an extremely narrow transmission peak the center of the stopband but its shape (a sharp triangle with a broad bottom) is not suitable for system design. Using standard coupled-mode theory together with transfer-matrix formalism, we show that by introducing several phase-shift regions and properly choosing their locations and magnitudes the transmission spectrum can be tailored into a nearly rectangular shape. For InP-InGaAsP based Bragg-grating filters estimates are made of achievable channel spacings in wavelength-division multiplexing systems 相似文献