FP干涉仪式光纤传声器数学模型

根据FP干涉仪式光纤传感器原理结构,通过分析敏感机理,采用声力电类比方法,得到FP干涉式光纤传声器等效线路图,并进一步综合光学、声学、电学、力学原理,得到了FP干涉式光纤传声器数学模型,并利用模型讨论了给定几何尺寸、材料参数下光纤传声器的灵敏度。通过模型预测光纤传声器的灵敏度可达280mV／Pa,制作的样机的灵敏度为240mV／Pa,模型预测的灵敏度与样机的灵敏度基本一致。该模型可以用来指导FP干涉式光纤传声器的研发,对其他类型的光纤传声器也有很好的借鉴作用。     

Application of ABCD Formalism in Theoretical and Experimental Analysis of Actively Modelocked Fiber Laser

Time domain ABCD matrix formalism is a useful model for analyzing the characteristics of actively modelocked fiber laser.Based on this model and given more consideration on the influences of optical fiber dispersion and optical fiber nonlinearity,the laser characteristic of actively modelocked fiber laser is analyzed,and the comparision of the theoretical analsis results with experimental ones is given.     

基于布里渊光频域分析技术的桥梁监测试验研究

布里渊光频域分析(Brillouin Optical Frequency Domain Analysis, BOFDA)技术是分布式光纤传感技术的一种。回顾了BOFDA的发展历史,介绍了BOFDA的最新应用进展情况,并提出了基于BOFDA测量桥梁挠度的新方法。通过光纤布设研究提出在桥梁底面采用全面粘贴的方式布设光纤,并分析了光纤应变表征桥梁挠度的理论,最后进行了基于BOFDA的室内桥梁模型测量试验研究。试验结果表明,百分表实测桥梁模型的挠度与桥梁模型上分级集中荷载及模型下表面的光纤应变变化均成正比例关系;BOFDA光纤应变可以标定桥梁模型变形范围,且光纤应变表征的桥梁模型挠度和百分表实测挠度值基本一致。因此,采用BOFDA技术进行桥梁挠度测量是可行的。     

光子晶体光纤陀螺热相位噪声研究

光子晶体光纤陀螺使用光子晶体光纤替代普通光纤绕制光纤环,是光纤陀螺的发展方向。光纤种类不同,其热相位噪声特性与传统陀螺存在差异。对光子晶体光纤陀螺光纤热相位噪声展开研究,利用有限元方法建立光纤模型及噪声模型,并搭建光源强度噪声抑制光路对热相位噪声进行测量,通过实验结果与仿真的对比,验证了模型的正确性。     

增益导引折射率反导引大模场光纤激光器特性分析

为了研究增益导引折射率反导引光纤激光器的功率分布及输出特性,根据此类光纤的结构原理和特点,建立了端面抽运的增益导引折射率反导引光纤激光器的基模光速率方程,推导了避免激发高阶模的增益阈值判决条件,并运用弦切法和Runge-Kutta法数值求解了该速率方程,分析了光纤长度、腔镜反射率等参量对基模输出功率的影响.采用芯径为1...     

一种级联喇曼光纤激光器数值模拟的新算法

为了优化设计光纤喇曼激光器的各项参量,采用喇曼激光器的基本理论模型模拟,提出了非线性最小二乘法和龙格-库塔法相结合的新算法,解决了模型中存在的两点边值问题,得到了级联喇曼光纤激光器的输出特性以及最佳光纤长度、激光阈值和斜率效率。结果表明,新算法非常有效,数值模拟的结果和相关实验相吻合。     

圆芯边孔光纤模式场分布和双折射的研究

对圆芯边孔光纤双折射的研究结果进行报道.使用有限元方法建立了包括计算圆芯边孔光纤横截面应力分布、折射率分布和双折射的模型,计算了圆芯边孔光纤的模式场分布、几何双折射和应力致双折射.研究表明,圆芯边孔光纤的应力致双折射很小,这是圆芯边孔光纤自身的特殊结构造成的.比较了几种不同边孔形状的光纤的双折射,提出了圆芯边孔光纤的优化结构.     

Alternative Gaussian spot size polynomial for use with doped fiberamplifiers

The validity of the usual Marcuse-Gaussian approximation for fiber modes is discussed in the context of doped fiber amplifiers and an proposed: ω/a=(0.616+1.66/V^1.5+0.987/V⁶). The polynomial's use is illustrated by extending the range of a simple Gaussian-based, numerical model of an erbium-doped fiber amplifier. Excellent agreement with a real-field-based model is demonstrated for practical fiber V values     

Principal Modes in Graded-Index Multimode Fiber in Presence of Spatial- and Polarization-Mode Coupling

Power-coupling models are inherently unable to describe certain mode coupling effects in multimode fiber (MMF) when using coherent sources at high bit rates, such as polarization dependence of the impulse response. We develop a field-coupling model for propagation in graded-index MMF, analogous to the principal-states model for polarization-mode dispersion in single-mode fiber. Our model allows computation of the fiber impulse response, given a launched electric-field profile and polarization. In order to model both spatial- and polarization-mode coupling, we divide a MMF into numerous short sections, each having random curvature and random angular orientation. The model can be described using only a few parameters, including fiber length, number of sections, and curvature variance. For each random realization of a MMF, we compute a propagation matrix, the principal modes (PMs), and corresponding group delays (GDs). When the curvature variance and fiber length are small (low-coupling regime), the GDs are close to their uncoupled values, and scale linearly with fiber length, while the PMs remain highly polarized. In this regime, our model reproduces the polarization dependence of the impulse response that is observed in silica MMF. When the curvature variance and fiber length are sufficiently large (high-coupling regime), the GD spread is reduced, and the GDs scale with the square root of the fiber length, while the PMs become depolarized. In this regime, our model is consistent with the reduced GD spread observed in plastic MMF.     

本征法布里-珀罗腔光纤压力传感器理论研究

建立了光子晶体光纤(PCF)型本征法布里-珀罗(F-P)腔光纤压力传感器压力响应理论模型,讨论了各参数对压力响应灵敏度的影响,给出了Matlab程序理论模拟结果。鉴于PCF焊接工艺的困难,提出了利用外径不同的单多模光纤熔接构成的改进型单多模光纤复合本征F-P腔光纤压力传感器结构,建立了压力响应理论模型,分析了提高压力响应灵敏度的关键参数,并模拟了光纤外径对压力响应灵敏度的影响。通过对两种本征F-P腔光纤压力传感器的比较分析看出,改进型结构无论在压力响应灵敏度还是制作难易度方面都颇具优势。     

脉冲光纤放大器中放大自发辐射对光纤储能的影响

在高功率脉冲光纤放大器中,由于增益介质长,抽运功率高,脉冲间隔产生的放大自发辐射(ASE)严重限制了光纤储能能力和可提取能量的提高。针对低重复频率、强抽运的条件,以稳态速率方程为理论基础建立了脉冲放大器模型,利用理论模型对脉冲放大器性能进行了分析,着重讨论了不同的数值孔径、激光功率填充因子、端面反射率、纤芯直径、光纤长度、抽运功率等参数对放大自发辐射的影响。讨论了光纤的储能、增益和可提取能量等的变化规律,给出了掺镱光纤中最大可提取的单脉冲能量以及放大器增益。     

ZEMAX在多模光纤准直器设计中的应用

利用ZEMAX软件进行多模光纤准直器的设计.在ZEMAX开发环境下建立多模光纤准直器光路系统的理论模型,通过人工优化的方法,设计并制作了可调焦的多模光纤准直器.仿真结果与实际结果相一致,证实了利用ZEMAX进行多模光纤准直器设计的可行性和准确性.利用所建立的模型,分析了各种因素对光纤准直器耦合效率和准直度的影响.     

波分复用系统的四波混频特性研究

本文对波分复用（WDM）光纤通信系统中的四波混频（FWM）特性进行了研究，得到了WDM可用于由多段不同长度，不同色散值的光纤组成的多级放大WDM系统FWM效应的计算方法，进而分析了单级、多级放大和色散补偿这3种特例的FWM特性，研究结果表明，标准单模光纤与高负色散值色散移位光纤的组合可以有效地抑制FWM混频效应。     

连续掺镱光纤放大器的提取效率

连续光纤激光器在加工及军事等领域都有重要应用。为了研究掺镱光纤放大器中影响提取效率的关键因素,在稳态激光速率方程基础上,考虑光纤放大器中自发辐射放大,建立了高功率光纤放大器的数值模型,并分析提取效率与光纤端面反射率,信号光功率以及抽运光功率之间的关系。采用反向抽运光纤放大器的实验方案,对有关提取效率的理论分析进行了初步验证。理论计算结果与实验验证结果的偏差小于10%。研究结果定性地描述了光纤端面反射率、信号光的功率和抽运光的功率对光纤放大器提取效率的影响。     

Evaluation of the cable model for electrical stimulation of unmyelinated nerve fibers

The cable model, used to calculate the membrane potential of an unmyelinated nerve fiber due to electrical stimulation, is reexamined under passive steady-state conditions. The validity of two of the assumptions of the cable model are evaluated, namely that the membrane potential be a function of the axial coordinate only and that the extracellular potential due to the presence of the nerve fiber be negligible. The membrane potential calculated from the passive steady-state cable model is compared with the membrane potential obtained from an analytical three-dimensional (3-D) volume conductor model of a nerve fiber. It is shown that for very small electrode-fiber distances (of only a few fiber radii), both assumptions are violated and the two models give quite different results. Over a wide range of the electrode-fiber distance (about 0.1 mm to 1 cm), both assumptions are fulfilled and the two models give approximately the same results. For very large distances (more than 10 cm, independent of fiber diameter) only the second assumption is satisfied, but a modification of the activating function of the cable model allows to calculate the membrane potential in agreement with the 3-D model.     

Stability and compression of pulses in the soliton laser

We present a theory of the soliton laser which examines how an external optical fiber enables a laser to produce shorter pulses than it could produce alone. We begin by discussing a phenomenological laser model which shows how the lower limit to the mode-locked pulse width can arise. This model is coupled to an external optical fiber cavity, into which a part of the output beam is launched. The returning pulse from the fiber cavity is then mixed with a circulating pulse in the laser at the output mirror. We have found stable solutions which are nearly periodic in the external cavity. We also find more than one solution for a given set of model parameters, depending on the initial conditions. The radiation (non-soliton) part of the propagation in the optical fiber cannot be ignored. It acts as a buffer between the tendency of the fiber to produce solitons, and the fact that a pure soliton is not an exact fixed point of the laser model.     

Analysis of fiber directional couplers and coupler half-blocksusing a new simple model for single-mode fibers

A model for a step-index fiber in the form of an equivalent slab guiding structure is presented. This model simplifies the analysis of fiber directional couplers and coupler half-blocks with dielectric and metallic superstrates. Simple empirical formulas to obtain the model parameters are also given. The use of this model is illustrated with some numerical examples     

单模Er3+／Yb3+共掺双包层光纤上转换效应实验研究

为了研究单模Er³⁺／Yb³⁺共掺双包层光纤中的上转换效应,采用对比实验的方法,用荧光分光光度计测量了单模Er³⁺／Yb³⁺共掺双包层光纤的绿色荧光,并与掺Yb³⁺光纤的绿色荧光进行了对比分析。得到Er³⁺／Yb³⁺共掺双包层光纤中的绿色荧光仍然是Er³⁺离子激发态吸收所产生,而Yb³⁺只起到能量搬运作用的结果。结果表明,两种光纤受激产生的荧光光谱、功率及其随抽运功率的变化关系,都遵循不同规律。     

Polarization fluctuations in a single-mode optical fiber

Polarization fluctuation characteristics of single-mode optical fiber output are examined theoretically and experimentally. A fiber model for studying these characteristics from the perspective of probability on the Poinare sphere is proposed. The relationship of the degree of polarization fluctuation to time and fiber length is shown theoretically. Measurements of submarine and underground cables and long-haul fibers up to 270 km in length generally support the proposed model     

Er3+/Yb3+共掺双包层光纤与掺Yb3+光纤中上转换效应实验研究

报道了Er3+/Yb3+共掺双包层光纤中由于上转换效应产生的荧光现象,并将此荧光与掺Yb3+光纤中产生的绿色荧光进行了详细测量和对比分析,结果表明,Er3+/Yb3+共掺双包层光纤中的绿色荧光仍然是Er3+离子激发态吸收所产生,而Yb3+只起到能量搬运的作用,两种光纤受激产生的荧光光谱、功率,及其随泵浦功率的变化关系,都遵循不同规律。