Dispersion compensation using only fiber Bragg gratings

Efficient and low cost dispersion compensation is necessary to achieve useful transmission distances in optical communication systems at bit rates above 10 Gb/s. In the paper, we present a novel method for dispersion compensation that uses three fiber gratings in series. This method eliminates the requirement for an optical circulator, commonly used in grating-based dispersion compensators. As a result, our device is inexpensive to fabricate and have a low insertion loss. We present a theoretical model that predicts how the efficiency of the device can be maximized. We also present experimental results showing complete dispersion compensation for 30-ps pulses, broadened to 67 ps by propagating through 10 km of standard, singlemode fiber     

Highly accurate temperature sensor using two fiber Bragg gratings

A new highly accurate temperature sensor for biomedical applications is proposed. The sensor, including two fiber Bragg gratings with different thermal coefficients, can accurately measure temperature with little laser frequency stabilization. A general theoretical model is established and the performance is analyzed. Some numerical examples from 0.1 °C to 10 °C temperature shift around human body temperature are presented. The novel method immunizes temperature sensing against the frequency drifting of the light source     

Novel multimode fiber for narrow-band Bragg gratings

We propose a novel multimode fiber structure with modal propagation characteristics tailored to facilitate the creation of narrow-band high-reflectivity fiber Bragg gratings. The fiber structure proposed consists of concentric cylindrical shells of higher and lower refractive index material. A full vector second-order finite-element method is used to analyze the proposed multimode fiber structure. Simulations of the modal profiles show that high-order modes are localized to particular high-refractive index shells. We present the theoretical characterization of the modal propagation constant as a function of inner shell radius, shell separation, and harmonic-mode parameter. It is shown that a fiber with a minimum inner shell radius of at least 25λ (where λ is the vacuum wavelength), and a minimum shell separation of at least 10λ provides a reasonable tradeoff between fiber size and grating performance. A simulation of the multimode fiber grating shows that a grating with a full-width at half-maximum bandwidth on the order of 10^-4λ is theoretically possible, if optical power is launched strictly into modes with angular harmonic parameter p=1     

Chirped fiber Bragg gratings for electrically tunable time delay lines

In this paper, a continuously variable delay line for phased array antennas is presented. The proposed delay line operates at a single wavelength and is based on properly designed linearly chirped fiber Bragg gratings. Continuous true time delay can be achieved by changing the temperature or strain along the grating region. Numerical results show that the delay line can be used for wide-band beamforming at radio frequencies up to 30 GHz with 1 ps as minimum time delay.     

Design and performance of high-speed optical pulse-code generatorsusing optical fiber Bragg gratings

The application of optical fiber Bragg grating filters to all-optical pulse-code generation was investigated. We report the design, fabrication, and testing of Bragg grating structures that convert a single picosecond input pulse into a train of output pulses, each with defined amplitude and timing. Experimental results are presented in which single 1.8 ps input pulses from a mode-locked fiber laser were efficiently converted into a “1101” optical codeword comprising a train of similar pulses, each separated by 11.1 ps     

Arrayed waveguide gratings, fiber Bragg gratings, and photonic crystals: an isomorphic Fourier transform light propagation analysis

In this paper, we present a unified Fourier transform (FT) approach to the study of arrayed waveguide grating (AWG), fiber Bragg grating (FBG), and photonic crystal (PC) devices. This methodology allows the design characteristics of transverse (AWG) geometries to be mapped on to longitudinal (or distributed) FBG and PC structures, due to a comprehensive isomorphism between these important passive optical grating-based devices. The unified approach presented here, which is based upon a modified Debye-Waller approach to the analytical solution of the coupled-mode equations, allows intuitive, yet accurate appraisal of arbitrary strength coupled structures. Exploiting this isomorphism, we relate our theoretical work to a number of practical cases. For example, we describe an FBG carousel configuration (analogous to a chirped AWG cascade) offering virtually ripple-free third-order dispersion compensation of 6.61 ps/nm/sup 2/ over a 100-GHz bandwidth.     

Chirped fiber Bragg gratings for WDM chromatic dispersioncompensation in multispan 10-Gb/s transmission

We report here the fabrication of fiber chromatic dispersion compensators, along with the tests of those components in wavelength-division-multiplexed transmission at 10 Gb/s and an analysis of their performance by simulation     

All‐optical multi‐wavelength header recognition using superimposed Bragg gratings based correlators

We have demonstrated that an optical correlator, based on superimposed Bragg gratings, can be used as all‐optical multi‐wavelength header recognition in optical packet switching networks. The proposed correlator is composed of two superimposed gratings in conjunction with variable delay lines. These superimposed Bragg gratings are used to demultiplex and multiplex the wavelength components of multi‐wavelength header bit patterns. The variable delay lines create a wavelength profile that can be matched with any arbitrary bit patterns. Simulation results for all optical recognition of four‐bit patterns at 10 Gbps are reported. The results show that when the header bit pattern matches the wavelength profile of the correlator, the generated auto‐correlation function will include a high amplitude peak; otherwise, a cross‐correlation function with low amplitude peaks will be generated in the output of the correlator. Considering this idea, multi‐wavelength header is recognized by using all‐optical processing method. Copyright © 2012 John Wiley & Sons, Ltd.     

FMCW multiplexing of fiber Bragg grating sensors

We report on the use of frequency-modulated continuous wave (FMCW) techniques for multiplexing fiber Bragg grating (FBG) sensors. This technique is based on the modulation of light intensity from a broadband source by a linear swept-frequency RF carrier. Signals from the FBG sensors located at different positions in an array are separated in frequency domain and demodulated using a tunable optical filter. The potential and limitation of the technique are discussed. A three-sensor FMCW multiplexed FBG array of parallel topology and a six-sensor hybrid FMCW/WDM system were experimentally demonstrated with -30 dB crosstalk between sensors and 2 με resolution in terms of root mean square (RMS) strain value     

光纤纵差保护中数据同步的误差分析及补偿办法

针对光纤差动保护中的通道及数据传输问题进行了讨论 ,提出了解决保护两侧采样同步问题的方案 :以采样时刻调整法结合不平衡输出抬高动作门槛     

光纤纵差保护中数据同步的误差分析及补偿办法

针对光纤差动保护中的通道及数据传输问题进行了讨论,提出了解决保护两侧采样同步问题的方案:以采样时刻调整法结合不平衡输出抬高动作门槛.     

A compensation scheme for CVT transient effects using artificial neural network

Capacitive voltage transformers (CVTs) provide instrument-level voltage signals to meters and protective relays in high voltage (HV) systems. The transients in CVTs could lead to protective relay mal-operation. This paper proposes the use of an artificial neural network (ANN) scheme to correct CVT secondary waveform distortions due to CVT transient. This is accomplished by using samples of voltage signals to achieve a good approximation of the inverse transfer function of CVTs, thus an accurate estimation of the primary voltages. Simulations are performed and the impacts of different parameters are studied. Performance results show that the proposed scheme is accurate and reliable. The proposed scheme can also be implemented on a digital signal processor board for real-time application.     

光纤光栅应变传感器温度补偿

光纤光栅传感器在应变测量方面有着非常广泛的应用。但在测量过程中受温度和应变两种因素的影响,常会导致测量结果的准确度受到一定程度的影响, 不能很好的满足实际需要。采用BP神经网络算法,通过实验样本训练建立神经网络结构,来降低温度对测量结果误差的影响。通过实验验证,在整个传感器温度测量范围内,使用BP神经网络可以有效的降低由温度引起的最大测量误差,使误差可以控制在一定范围内,对传感器的使用具有重要意义。     

高精度光纤光栅振动解调系统研究与应用

为实现工程系统中对振动信号的检测,提出了一种基于衍射光栅的光纤布拉格光栅(FBG)振动解调系统。解调系统通过色散成像原理获取传感器反射光谱,由所设计的嵌入式单元进行信号处理,并通过专用的上位机解调软件完成数据处理与分析。将系统封装为解调仪器,能实际应用于振动信号的探测。所设计的系统波长解调范围为1 525～1 570 nm,波长重复性可达±1 pm,分辨率为0.5 pm,可实现8通道复用测量,最高光谱解调速度可达10 kHz。实验结果表明,该FBG振动解调系统能够高精度测量不同频率与幅度的振动信号,最小可探测应变约为0.319με/Hz^1/2,在结构安全监测等领域具有重要的应用前景。     

Design of arrayed-waveguide gratings using hybrid Fourier-Fresneltransform techniques

We describe how transform techniques may be applied to the design of arrayed-waveguide gratings (AWG's). A hybrid Fourier-Fresnel transform model indicates that a flat AWG router passband over 30% of the device free-spectral range (FSR) is feasible. Minimized passband ripple is achieved by applying a subparabolic phase-profile (phase-exponent P=1.82) to the Fourier plane of the AWG. Simulations of a complex-apodized AWG with passband 3 dB width increased from 1 to 12 nm, with a near-trapezoidal amplitude response, and band-edge group delay of 70 ps reduced to 10 ps are presented for a device with a FSR of 40 nm     

利用 GWO-LSSVM 算法对光纤压力传感器进行温度补偿

光纤压力传感器工作性能受温度影响较大,需进行温度补偿。针对这一问题,提出了灰狼算法与最小二乘支持向量机(GWO-LSSVM)算法相结合的软件补偿方案,利用灰狼算法在指定范围内迭代优化最小二乘支持向量机的惩罚因子ζ和核参数σ以求构建补偿算法模型。在不同温度环境下,对传感器进行标定试验测得传感器的输入输出数据,分成测试集和训练集。以测试集的预测值计算的均方根误差为适应度函数,将温度补偿问题转化为带约束的凸二次优化问题。结果表明,相较于补偿前,温度补偿后的光纤压力传感器的灵敏度温度系数由9.405×10^-3/℃提升到1.201 6×10^-4/℃,温度附加误差相对值由28.215%提升到0.481%,传感器的温度稳定性得到了很大程度的改善。     

继电保护光纤通道仿真测试及研究

随着光纤电流差动保护在电力系统中的广泛应用,实际运行中暴露出越来越多的新问题,其中由于缺乏针对光纤通道的各种误码工况的仿真测试及试验,光纤电流差动保护在通道延时、误码工况下的动作行为和动作性能没有办法进行试验和验证,针对光纤电流差动保护应用的实际情况设计出了仿真测试装置,并介绍了其实现功能、硬件设计和应用。     

光纤保护通道配置

在超高压电力线路中配置双套纵联继电保护装置，是快速排除电力系统故障，使之安全、畅通的必要保障。论文着重对利用光纤通道传输纵联保护数据信号的两种主要传输方式和技术特点作了详细的论述和比较；并以沙芙超高压电缆线路中所选择的光纤保护及通道配置方案为例，分析了作者在参加此项工作所取得的经验及体会。     

FC协议测试卡的软件设计与实现

随着FC技术在航空电子、网络数据存储、高速IP网络等领域得到大量应用和发展,急需针对FC网络与设备的测试手段,FC协议测试设备应运而生。采用FPGA技术设计的基于CPCI总线的FC协议测试卡,可灵活地插入工控机中,配合其测试软件,构成1台FC协议测试仪。它实现了FC协议数据发生、捕获分析、性能统计、比特误码测试等多种功能,可对FC网络及设备进行全面的测试,为FC设备的开发与网络的运行提供测试保障。详细阐述了FC协议测试卡的软件设计方案及实现。