光纤光栅带内色散特性的离散时域分析

采用多层介质的离散传输线模型表型光纤光栅响应特性，并利用数字信号处理方法对光纤光栅的相位特性进行了分析，研究了用于密集波分复用窄带滤波的变迹光纤光栅的带内色散特性，表明对称变迹光纤光栅的幅度响应与相位响应之间满足希尔伯特变换关系，幅度响应越接近理想的矩形，带内色散越大。并采用耦合模理论数值计算了对称变迹的光纤光栅的反射相位响应和带内群时延情况，验证了分析结果。     

Asymmetrically Apodized Fiber Bragg Gratings for Applications in Dispersion-Less Fabry-Pérot Fiber Cavities

Abstract

This article presents a theoretical study of the dispersion properties of the asymmetrically apodized fiber Bragg gratings. It is shown that the dispersive behavior of these gratings may be changed from normal to anomalous, depending on the apodization function and the grating strength. The asymmetrical Bessel functions were chosen in order to demonstrate these properties of the gratings. The application of this effect in a dispersion-less Fabry-Pérot fiber cavity formed by two asymmetrically apodized fiber Bragg gratings is discussed.     

A novel method for fabricating apodized fiber Bragg gratings

In this paper, a new implementation of the double exposure method for fabricating apodized fiber Bragg gratings by controlling the parameters of rotation stage and the number of UV-shots is presented. As a result, the average refractive index is kept nearly constant along the Bragg grating, and various apodized fiber Bragg grating with high reflectivity and high side lobe suppression ratio have been fabricated in single-mode hydrogen-loaded photosensitive fiber . The achieved side-lobe suppression ratio is larger than 25 dB.     

切趾技术对光纤布拉格光栅法布里-珀罗滤波器反射特性优化的研究

利用矩阵分析法,针对两个相同光栅构成的光纤布拉格光栅法布里-珀罗(F-P)腔滤波器进行理论分析。数值模拟分析了光栅长度变化对光栅以及F-P腔滤波器反射特性的影响,指出光栅长度增加对反射特性影响的优缺点,分析利用常用切趾函数对光栅进行切趾,减小由于光栅长度增加导致反射谱的的旁瓣增大,对组成的F-P腔滤波器的反射特性的优化,得到了光栅切趾对F-P腔滤波器的反射特性的影响规律。对于在实际应用中制作出性能优良的光纤布拉格光栅F-P腔滤波器有一定的参考价值。     

Modeling and Testing of Uniform Fiber Bragg Gratings Using 1-D Photonic Bandgap Structures in Microstrip Technology

A way to model and test fiber gratings and fiber grating-based systems in the microwave range is proposed. The method rests on the equivalence relationship found between a fiber grating and a one-dimensional microstrip photonic bandgap structure that consists of a periodic pattern of circles etched in its ground plane. The equivalence assures that the frequency-response of the fiber grating is an upshifted replica of the corresponding frequency to its equivalent microstrip device. Both apodized and nonapodized uniform fiber gratings have been considered and the feasibility of the proposed method has been shown in simulation and measurement.     

Modeling and Testing of Uniform Fiber Bragg Gratings Using 1-D Photonic Bandgap Structures in Microstrip Technology

A way to model and test fiber gratings and fiber grating-based systems in the microwave range is proposed. The method rests on the equivalence relationship found between a fiber grating and a one-dimensional microstrip photonic bandgap structure that consists of a periodic pattern of circles etched in its ground plane. The equivalence assures that the frequency-response of the fiber grating is an upshifted replica of the corresponding frequency to its equivalent microstrip device. Both apodized and nonapodized uniform fiber gratings have been considered and the feasibility of the proposed method has been shown in simulation and measurement.     

Spectral characterization of fiber gratings with high resolution

We demonstrate a high-resolution technique to measure the optical magnitude and phase responses of fiber gratings. The technique employs single-sideband modulation of an optical source and has spectral resolution in the hertz regime. The technique is demonstrated by measurement of the phase ripples of unapodized and apodized chirped gratings as well as the transmission spectrum of a pi-phase-shifted grating. Although it is demonstrated on fiber gratings, the technique is applicable to any optical device.     

弱双折射光纤布喇格光栅反射偏振对温度响应特性的研究

理论分析了切趾弱双折射光纤布喇格光栅反射偏振相关特性与温度之间的关系.数值模拟了切趾弱双折射光纤光栅的反射谱、偏振相关损耗和差分群时延随波长变化曲线.实验测出了不同温度下反射谱、偏振相关损耗和差分群时延随波长变化曲线.根据实验结果对偏振相关损耗和差分群时延的变化情况作出了分析.反射偏振相关损耗呈现两个峰值,随温度增加两峰漂移程度相同,表明偏振相关损耗无明显差异.差分群时延最大值随温度增加成线性向长波方向漂移,证明了光纤光栅正交模损耗变化的等同性.综合理论分析与实验结果表明:切趾弱双折射光纤布喇格光栅的偏振特性随温度产生明显的变化,其正交模变化呈现等比例特性.     

The research on temperature measurement based on polarization dependent loss

This paper analyzes the properties of reflected polarization dependent loss of apodized fiber Bragg gratings with temperature effective. We simulates reflected spectrum and polarization dependent loss of the apodized fiber Bragg gratings. The reflected spectrum and polarization dependent loss are measured under different temperatures. The analysis results show that reflected polarization dependent loss presents two peaks which shift an equal proportion to long wavelength with temperature increasing and have very good stability so we propose an idea that use polarization dependent loss as temperature sensor measurement parameters. The results show that the accuracy of measurement can be increased almost by one order of magnitude.     

Apodised fiber Bragg gratings fabricated with a uniform phase mask using Gaussian beam laser

A new exposure scheme for fabricating apodised fiber Bragg gratings by the use of a uniform phase mask and a Gaussian beam laser is demonstrated. Average refractive index is kept nearly constant along the grating to derive a side lobe suppression of 20 dB in the shorter wavelength. This scheme allows the writing of truly apodized fiber Bragg gratings.     

Asymmetrically Apodized Linearly Chirped Fiber Bragg Gratings for Efficient Pulse Compression

Asymmetrically apodized linearly chirped fiber Bragg gratings (FBGs) are shown to have highly linearized time-delay response. In simulations of a five-stage, 5-cm grating-based dispersion compensation system, asymmetrically apodized FBGs are shown to give over 60% reduction in the energy scattered from the main pulse body, 16 ps?60 ps pulses propagated over 800 km, as compared to a symmetrically apodized grating of similar length, strength, and bandwidth.     

相移长周期光栅长度切趾光谱特性

应用耦合模理论和传输矩阵法分析了长周期相移光栅的光谱特性,比较了折射率切趾和长度切趾所产生的不同光谱结构,并分析了长度切趾中不同的切趾函数及光栅长度对光谱结构的影响.讨论了长度切趾的旁瓣增强效应,发现了一些新的有益结果.     

啁啾双光纤光栅群时延特性

研究了变迹线性啁啾双光纤光栅的群时延特性及其在高次色散补偿中的应用.分析表明,群时延特性与周期差ΔΛ和不同的啁啾参量C有很大的关系.研究结果表明啁啾双光纤光栅在高次色散补偿和光纤CDMA中有应用价值.     

Extracting the structure of highly reflecting fiber Bragg gratings by measuring both the transmission and the reflection spectra

We demonstrate a novel method that enables one to measure the structure of highly reflecting fiber Bragg gratings. The method is based on measuring both the transmission and reflection spectra of the grating and applying an inverse-scattering algorithm. The use of the transmission spectrum significantly reduces the sensitivity of the reconstruction to measurement noise, and therefore it significantly decreases the measurement duration. We experimentally demonstrate our method for reconstructing the structure of an apodized grating with a reflectivity of 99.91%.     

Fiber Bragg gratings for dispersion compensation in optical communication systems

This paper presents an overview of fiber Bragg gratings (FBGs) fabrication principles and applications with emphasis on the chirped FBG used for dispersion compensation in high-speed optical communication systems. We discuss the range of FBG parameters enabled by current fabrication methods, as well as the relation between the accuracy of FBG parameters and the performance of FBG-based dispersion compensators. We describe the theory of the group delay ripple (GDR) generated by apodized chirped fiber gratings using the analogy between noisy gratings and superstructure Bragg gratings. This analysis predicts the fundamental cutoff of the high frequency spatial noise of grating parameters in excellent agreement with the experimental data. We review the iterative GDR correction technique, which further improves the FBG quality and potentially enables consistent fabrication of FBG-based dispersion compensators and tunable dispersion compensators with unprecedented performance.     

适合于有线电视系统的色散补偿光纤光栅

分析了光栅色散抖动对有线电视信号的影响,估计出落在信号50MHz-5550MHz范围内互调产物功率约占所有互调产物功率的10％－50％,为了抑制色散抖动幅度,光栅的折射率变化应该从初值零渐渐长到最大值。长度为10cm,包络为升余弦与tanh(4z)的光栅都能满足有线电视系统的要求,此外还发现,长光栅对应的抖动周期小,因此对信号的影响也小,具有升余弦包络的光栅比tanh(4z)光栅更能有效地抑制色散抖动。     

High-Accuracy Measurement of the Dispersion of Chirped Fiber Gratings

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长周期光纤光栅的分析和优化设计

利用传输矩阵法对相移和变迹长周期光纤光栅的传输特性进行了计算和分析,提出长周期光纤光栅传输谱的相移优化设计方法.采用非均匀相移的设计思想,优化长周期光纤光栅的传输谱.和传统的均匀相移和变迹长周期光纤光栅相比,可以有效消除长周期光纤光栅谐振波长附近的旁瓣,并保证其传输性能.计算和分析结果表明:这种方法比传统的变迹优化设计方法更有效.     

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.