Flexible Optical Waveguide Bent Loss Attenuation Effects Analysis and Modeling Application to an Intrinsic Optical Fiber Temperature Sensor

The temperature dependence of the bending loss light energy in multimode optical fibers is reported and analyzed. The work described in this paper aims to extend an initial previous analysis concerning planar optical waveguides, light energy loss, to circular optical waveguides. The paper also presents à novel intrinsic fiber optic sensing device base on this study allowing to measure temperatures parameters. The simulation results are validated theoretically in the case of silica/silicone optical fiber. A comparison is done between results obtained with an optical fiber and the results obtained from the previous curved optical planar waveguide study. It is showed that the bending losses and the temperature measurement range depend on the curvature radius of an optical fiber or waveguide and the kind of the optical waveguide on which the sensing process is implemented.

Evaluation of the Bending Loss of the Hollow Optical Fiber for Application of the Carbon Dioxide Laser to Endoscopic Therapy

Since carbon dioxide laser is excellent for incision, hemostasis, coagulation, and vaporization of soft tissues, it has been widely applied in clinical treatments as the laser knife. In these days, flexible thin hollow optical fibers transmitting mid-infrared light have been developed, and the application of carbon dioxide laser to endoscopic therapy has become possible. However, it is expected that the irradiation effect is influenced by the change in the laser power at the tip of the hollow optical fiber due to the change in the transmittance by the bending loss. The purpose of this research is to quantitatively evaluate the change in the output power and therapeutic effect by bending the hollow optical fiber in a gastrointestinal endoscope. The change in the transmittance of the hollow optical fiber due to the insertion of the fiber into the endoscope and bending of the head of the endoscope was measured. Then, the relationship between the irradiated laser power and the incision depth for a porcine stomach was investigated. As the results, the most significant decrease in the transmittance of the hollow optical fiber was caused by the insertion of the fiber into the instrument channel of the endoscope, and bending of the head of the endoscope with the angle of 90° decreased the output laser power and incision depth by 10% and 25%, respectively. Therefore, it was confirmed that the bending loss of the hollow optical fiber due to the bending of the head of the endoscope had no significant influence on the endoscopic therapy using the carbon dioxide laser.

Influences of polishing on return loss of optical fiber connectors

With Al2O3 and SiO2 as polishing medium, under different polishing conditions, e.g. with different polishing pressure, polishing time and polishing fluid, the influences of polishing treatment on the return loss of optical fiber connectors were investigated. The return loss of optical fiber connectors is 32CD*238dB before polishing. The results show that dry polishing（i.e. no polishing fluid） with Al2O3 has less influence on return loss of optical fiber connectors, while dry polishing with SiO2 reduces return loss to about 20dB because of the end-face of optical fiber contaminated. The wet polishing（i.e. using distilled water as polishing fluid） with Al2O3 or SiO2 can increase return loss to 45CD*250dB, but wet polishing with Al2O3 may produce optical fiber undercut depth of 80CD*2140nm. Wet polishing with SiO2 should be preferentially selected for optical fiber connectors and polishing time should be controlled within 20CD*230s.

Research on Additional Loss of Guidance Optical Fiber

The factors which cause additional losses of guidance optical fiber in wound state were analyzed.A mathematical model used to analyze the macro-bend losses in the cross region producing in the precision winding process was established.For an actual guidance optical fiber,the measured data of the fiber's additional losses under low temperature and the loss curves with radius were given in the paper.The simulation results were compared with the test data.It shows that the additional losses of optical fiber caused by bending and low temperature can meet the actual requirements of the fiber optical guidance system.The established model can be used to predict the change trend of fiber losses in the winding process with a certain tensile force.

Research on Special Optical Fiber under Radiation

The variation of optical spectrum of some special fibers under radiation is studied in this paper. We discuss the loss of optical fiber under the influence of radiation. It shown that the colourated positive ions in the silica fiber core is harmful(i.e. Fe, Cr, Mn, Cu, Co, Ni). In the visible band and near area(0.35μm～0.85μm), the spectral distribution of the common silica fiber is dependent on the radiation total dose and spectral curves of the particular double clad optical fiber is unchanged after the radiation.

OPTIMIZATION OF WDM OPTICAL PACKET SWITCHES WITH SPARSE WAVELENGTH CONVERTERS AND NON-DEGENERATE FIBER DELAY-LINES

This paper investigates the untraditional approach of contention resolution in Wavelength Division Multiplexing (WDM) Optical Packet Switching (OPS). The most striking characteristics of the developed switch architecture are: (1) Contention resolution is achieved by a combined sharing of Fiber Delay-Lines (FDLs) and Tunable Optical Wavelength Converters (TOWCs); (2) FDLs are arranged in non-degenerate form, i.e., non-uniform distribution of the delay lines; (3) TOWCs just can perform wavelength conversion in partial continuous wavelength channels, i.e., sparse wavelength conversion. The concrete configurations of FDLs and TOWCs are described and analyzed under non-bursty and bursty traffic scenarios. Simulation results demonstrate that for a prefixed packet loss probability constraint, e.g., 10-6, the developed architecture provides a different point of view in OPS design. That is, combined sharing of FDLs and TOWCs can, effectively, obtain a good tradeoff between the switch size and the cost, and TOWCs which are achieved in sparse form can also decrease the implementing complexity.

高阶轨道角动量传输光纤设计及传输特性研究(内封底文章)

为解决一般轨道角动量传输光纤传输轨道角动量模式数量少、质量差的问题,提出了一种基于正六边形空气孔排列的新型光子晶体光纤结构。该光纤引入了空气填充率高的矩形空气孔以及采用高折射率材料填充环形传输区域,能够有效提高环形传输区域和包层间的折射率差,且正六边形排列空气孔有利于提高模间有效折射率差。经过结构优化得到最优光纤结构,有限元法的分析结果表明,最优结构下,该光纤在常用波段S+C+L+U波段上能够支持142种轨道角动量模式的传输,最高阶数达到36阶。且所提出光纤具有良好的传输特性,本征模式的最高限制性损耗为10−9 dB/m量级,与典型轨道角动量传输光子晶体光纤相比至少降低了一个数量级;最大有效模场面积能够达到206.18μm^(2),最小非线性系数低至0.397 W^(−1)∙km^(−1);色散平坦且最小色散变化低至1.4578 ps/(nm∙km);所有本征模式纯度均在93.4%~96.8%范围内。且该光纤具有较好的制备可行性,对制造精度要求不高。因此,该光纤在基于轨道角动量光纤的复用系统中具有广阔的应用前景,为提高通信容量提供了一种有效手段。

Sn-Zn合金包覆PAN基碳纤维/聚六氟丙烯有机光纤材料的制备

采用Sn-Zn合金包覆聚丙烯腈(PAN)基碳纤维,以聚六氟丙烯为载体制备塑料光纤(POF)皮层材料,并将POF皮层材料与聚苯乙烯光纤芯材进行匹配,研究了材料在力学性能、传输损耗性、光场强度方面的变化。结果表明:Sn-Zn合金表面包覆PAN基碳纤维与聚六氟丙烯结合紧密,作为POF皮层材料的效果良好,在最常见的650 nm波长、100 m内,传输低于100 Mb/s速率数据信息的能力符合要求,光信号基本环绕着光纤芯材传播,没有过多的光信号因为皮层材质的缘故而散失,表明该皮层材料与聚苯乙烯光纤芯材的匹配性较高。

面向通感一体系统的耐弯三芯光纤

为了同时兼顾狭小空间下的光纤数据通信与环境感知,设计并制备了一种面向通感一体系统的耐弯三芯光纤。该光纤采用三角形纤芯排布和深掺氟折射率沟道结构,标准外径为125μm,优化了O波段(1260~1360 nm)的传输特性,具有与G.657.A1光纤相似的布里渊增益谱(BGS)分布。测试结果表明:在1310 nm波长处,芯层的平均损耗为0.58 dB/km,平均芯间串扰低于-50 dB/km;当最小弯曲半径R=10 mm且缠绕50圈时,光纤的弯曲损耗低于0.1 dB。

物联网环境下光纤通信网络总线链路丢包率推断

光纤通信网络总线链路在应用过程中容易受到带宽限制,导致光纤通信网络链路丢包率检测精度差、推断效率低,不能满足用户数据传输需求。为此,提出物联网环境下光纤通信网络总线链路丢包率推断方法。根据光纤通信网络路由矩阵,获取物联网环境下光纤网络的通信状态,依据时序分析策略检测网络总线链路数据传输中的薄弱环节,分析不同时段间变量的关联性,建立线性回归模型,计算下个时段预测值,获取总线链路传输状态。计算每条线路的时空关联性,结合背景流量,采用最小二乘法推断链路丢包率。实验结果表明,所提方法的故障识别率高于95%,误差因子与相对误差在0.2和0.02以下,推断耗时低于2 ms,为光纤通信网络的数据传输提供参考。

Optimization of highly nonlinear dispersion-flattened photonic crystal fiber for supercontinuum generation

A simple type of photonic crystal fiber （PCF） for supercontinuum generation is proposed for the first time. The proposed PCF is composed of a solid silica core and a cladding with square lattice uniform elliptical air holes, which offers not only a large nonlinear coefficient but also a high birefringence and low leakage losses. The PCF with nonlinear coefficient as large as 46 W-1 · km-1 at the wavelength of 1.55 um and a total dispersion as low as ±2.5 ps. nm-1 · km -1 over an ultra-broad waveband range of the S-C-L band （wavelength from 1.46 um to 1.625 um） is optimized by adjusting its structure parameter, such as the lattice constant A, the air-filling fraction f, and the air-hole ellipticity η. The novel PCF with ultra-flattened dispersion, highly nonlinear coefficient, and nearly zero negative dispersion slope will offer a possibility of efficient super-continuum generation in telecommunication windows using a few ps pulses.

Improved all-optical OR logic gate based on combined Brillouin gain and loss in an optical fiber

Improved all-optical OR gates are proposed, using a novel fiber nonlinearity-based technique, based on the principles of combined Brillouin gain and loss in a polarization-maintaining fiber （PMF）. Switching contrasts are simulated to be between 82.4%-83.6%, for two respective configurations, and switching time is comparable to the phonon relaxation time in stimulated Brillouin scattering （SBS）.

Excess Loss of the Coupling System to Double-Function Optical Circulators Utilizing Lens Twice and Two-Fiber Tips

A new type of double function optical circulator for double fibers is proposed in this paper. Two fiber tips and lens twice are employed in this kind of device as the coupling system for what is believed to be the first time. Because two fiber tips and lens twice are used, the function of optical circulator is duplicated in comparison with conventional optical circulator with single fiber tip. Thus the optical circulator has a low cost and a small volume comparatively. Excess loss of the coupling system and the misalignment of the lens twice in angular error and the position error to the developed circulator are analyzed and discussed by using Gauss wave and double integral in theory. The analysis results show that the excess loss is zero when each distance is equal to f between every adjacent： fraction and without misalignment error in the coupling system. In addition, the excess loss is increasing with increment of the distance error and the angular error. The errors of the angular of the optical axis to lens and the distance between the SL to lens are the main source of the excess loss. The higher the errors are, the higher the excess loss is. It＇s very important for reducing the misalignment errors in the coupling system with high ratio of coupling to achieve low excess loss. Details of design and excess loss in the coupling system of this circulator are presented.

基于分布式光纤的松散含水层失水沉降规律研究

煤矿开采扰动间接引起的地下水散失会使松散层压缩,造成地表沉降,威胁煤矿安全生产。为深入分析此类非采动因素对松散含水层失水沉降的影响,根据已有的地质水文资料将研究区松散层自上而下划分为一含、一隔、二含、二隔、三含、三隔和四含。利用分布式光纤监测技术、水文观测技术和土力学实验对研究区域松散含水层进行全面观测,分析了非采动情形下各层位的形变特征,探究了深层隔水层的黏土弱化规律,明确了深层含水层形变量和该层位水头高度变化之间的关系。结果表明:①四含及上部部分隔水层持续压缩是造成研究区域地表沉降的主要原因。对地层形变贡献最大的两个层位分别为四含和一含,其中一含形变具有季节性特征,春季夏季抬升,秋季冬季沉降,而四含则在观测周期内呈持续沉降态势。②结合布设水文孔、分布式光纤和土力学实验,实现了对目标层位黏土弱化程度的监测,研究区四含上覆黏土层受四含地下水的影响产生黏土弱化,其弱化程度与埋深成反比,与地下水流通性成正比,黏土层弱化将导致含水层顶部隔水层压缩,加剧地表沉降。③四含形变与四含层位水头高度变化的趋势一致,两者呈线性关系,观测结果与理论计算结果相符,表明四含失水是造成四含压缩形变的主要原因。

光纤损耗谱工程全场景再现教学实验系统

光纤损耗特性是“光纤通信原理”课程必须要掌握的关键知识点。为了让学生更形象直观地学习损耗谱知识,本课程将工程测量和标定方法植入到课程实验教学中,利用工程全场景再现的理念,设计了一套全新的光纤损耗谱测量实验系统,系统测量光纤在700~1750 nm波长范围内的损耗谱,学生通过光路设计、连接、计算机拟合、绘制曲线等多个操作步骤,融入到工程实测场景中,更好地掌握光纤损耗理论知识。

面向太赫兹波段的负曲率光纤设计及数值研究

文章设计了一种基于环烯烃共聚物(cyclic olefin copolymer,COC)的空芯负曲率光纤(negative curvature fiber,NCF),分析结构参数光纤芯径、管径和毛细管厚度对光纤限制损耗的影响,并对参数进行优化,使得单包层NCF在2.0~2.5 THz频率范围内限制损耗为10^(-4)~10^(-5)dB/m,损耗最低值可降到8.90×10^(-5)dB/m;引入内包层管破坏常规负曲率光纤的对称性,使纤芯模式与内包层管壁模式进行耦合,从而增加x和y偏振方向的折射率和损耗差异产生双折射;对影响光纤双折射特性和限制损耗的因素进行分析,在2.0~3.0 THz频率范围内双折射系数可达到10^(-4)~10^(-5)。该文结果为太赫兹NCF的长距离传输、偏振敏感等应用提供了一条新的途径。

柔性掌指关节运动角度光纤传感器

现阶段手部康复训练中的运动监测主要针对手肘手腕等大关节,且柔性不足,为解决难以监测手部掌指关节运动角度的问题,基于光纤的宏弯损耗原理,设计并制作了一款可穿戴掌指关节运动角度传感器。首先分析掌指关节角度测量原理,结合光纤宏弯损耗特性,制作传感硅胶模块。开展实验对传感硅胶模块进行标定与验证,制作穿戴装置形成运动角度传感器。实验结果表明该传感器的测量范围为0~80°,验证曲线的Pearson相关系数为0.9987,0~70°范围内最大测量误差为2°,测量准确度高。该传感器制作成本低,对温度不敏感,抗电磁干扰能力强,满足实际应用需求,对手部运动角度实时监测与预测和动作识别具有重要的实用价值。

基于折射率匹配的光纤扩束互连插入损耗研究

为拓展光纤扩束互连的应用,建立了低损耗光纤扩束互连的耦合效率模型。设计了折射率过渡匹配光路,实现了光纤端面免镀膜;基于高斯光束理论和几何误差分析,采用蒙特卡罗模拟方法,仿真了各参量的插入损耗分布。经过16芯扩束连接器的样品制作和实验,随机互换插入损耗大于理论模型0.2d B,原因为额外FC/APC连接器增加了额外的插入损耗。验证了理论模型的有效性,满足了随机互换插入损耗小于0.8d B的要求。此研究方法对其它光器件的各零部件精度与耦合效率的评估有指导作用。

具有温度自补偿功能的宽频带光纤电场传感器

光纤电场传感器抗电磁干扰能力强、响应速度快,在电力设备运行状态和绝缘状况的监测领域有着广阔的应用前景。现有的光纤电场传感器由多个不同功能的分立光学器件组合而成,光路耦合对准困难、光功率损耗大、灵敏度低。此外,温度交叉敏感问题进一步限制了传感器的实际工程应用。为克服现有技术难题,提出一种以特种功能光纤取代分立光学器件,进而形成全光纤电场传感器的技术思路。传感器中的起偏器、检偏器、波片等功能器件均在光纤上实现,避免了分立元件之间对准、耦合等带来的传感器结构不稳定、性能低等问题。此外,通过双晶体正交级联光路结构的设计,赋予传感器温度自补偿功能,实现对温度交叉敏感的有效抑制。实验结果表明,传感器可同时对50 Hz低频电场和纳秒级脉冲电场进行有效捕获,环境温度变化给测量结果带来的误差仅为0.1%/℃。全光纤电场传感器结构简单、稳定性好、测量频带宽,在电力设备快速暂态过电压的测量方面有着重要的潜在应用价值。

大模场抗弯曲全固态光纤的结构设计

提出了一种具有对称结构的大模场面积和低弯曲损耗的新型结构光纤,运用全矢量有限元法结合完美匹配层边界条件分析了光纤特性。该光纤由纤芯中的梯形折射率环和包层中的多层下陷层组成,仿真结果显示该光纤具有低弯曲损耗大模场单模传输的特性。对比分析了梯形谐振环、矩形谐振环、三角形谐振环结构光纤的弯曲损耗以及电场模式分布,实验结果显示梯形折射率环更具优越性。多层下陷层结构将模场限制在纤芯中,下陷层的数量大于2时模场面积基本上保持不变。研究结果表明,在波长为1550 nm、弯曲半径为20 cm时,基模(FM)弯曲损耗只有0.056868 dB/m,而高阶模(HOMs)损耗为3.58 dB/m,有效模场面积可达2313.67μm^(2)。该光纤对弯曲方向不敏感,在高功率光纤激光器放大器等光通信器件领域具有广阔的发展前景。