Polarization maintaining optical fiber multi-intruder sensor

In this paper, an optical fiber multi-intruder sensor based on polarization maintaining optical fiber (PMF), without any interferometric fiber loop, is introduced. To map the local coordinates of intruders on the beating spectrum of the output modes, radiation from a ramp frequency modulated laser is injected at the input of PMF optical fiber sensor. It is shown that the local coordinates and some characteristics of intruders can be obtained by the measurement of the frequencies and amplitudes of the output mode beating spectrum. Generally the number of beating frequencies is more than the number of intruders. Among the beating frequencies, a group with maximum signal to noise ratio is chosen. The short Fourier denoising method is employed to increase the sensor resolution. Because the output signal is the superposition of finite numbers of discrete frequencies this method is a powerful tool for denoising even for negative signal to noise ratio.     

POTDR分布式光纤传感及其在安防监测中的应用

提出了一种基于偏振光时域反射计分布式光纤传感技术的新型安防监测系统.该系统使用偏振分束器获取到具有正交偏振态的两路偏振光时域反射计信号,对比验证以确认是否出现了造成偏振态变化的扰动,提高了系统对扰动远程定位检测的准确度,大幅度减小了误判率和漏报率.同时在偏振光时域反射计系统的扰动探测中创造性的采用差值法和相对坐标相结合的方法,首次可以明显并且直观地检测和定位偏振光时域反射计系统中的扰动.最后采用Visual C++开发了一套实时的数据采集与处理软件.实验结果表明该系统具有较高的灵敏度,并在2 km和14 km处获取到具有较高信噪比的扰动信号.     

Optical fiber cables using V-grooved cylindrical units: High performance cables

Some practical and theoretical aspects of a V-grooved cylindrical cable (high performance optical fiber cable) are now being developed in several countries. Design of cables is important, because bendings may cause distortions. In order to limit micro-bending losses in an optical fiber cable, it is possible to modify parameters relating to the fiber or the cable. Some of the possibilities are: to decrease the core diameter in order to decrease the attenuation coefficient; to increase the diameter of the cladding so as to increase the tension above which micro-bendings occur; to increase the continuous bending radius due to cabling; to decrease the effects of roughness (μ); to integrate the effects of roughness as much as possible by decreasing the Young modulus of the coating and of the cable material and by increasing the cladding thickness; and to suppress the tension T of the fiber in the cable. The cabling element is made of a V-grooved cylindrical core, in which the fiber with an outside diameter d_e (outside diameter or primary coating) are laid without tension, with a slight excess length. The slots with a depth h are helical or alternated helical, providing the possibility of additional excess length, and the fiber can be “cabled” directly without stresses. A central strength member with a diameter Dp reinforces the cylindrical rod, ensuring the mechanical and thermal qualities.     

内封光纤高温超导CORC©缆线电磁特性仿真研究

内封光纤高温超导 CORC?? (Conductor on Round Core) 缆线在传统 CORC?? 缆线结构的基础上, 将光纤嵌于铜芯骨架内, 不仅能够保持原有集束缆线表面形貌的完整性, 还能通过外置分布式光纤传感解调设备, 实现对缆线失超的快速检测. 然而, 改变缆线结构有可能引起缆线电磁特性发生变化, 继而影响高场磁体的设计与应用. 本文以高温超导CORC?? 缆线为研究对象, 采用有限元仿真技术研究了直流供电的内封光纤CORC?? 缆线在正常运行工况下的电磁场分布特性, 通过对比普通CORC?? 缆线, 分析了内封光纤对CORC?? 缆线电磁性能产生的影响. 研究结果表明, 两种缆线在正常运行工况下的电流密度及磁通密度分布特性较一致, 初步论证了内封光纤高温超导CORC?? 缆线在高场磁体应用的可行性.     

Optical fiber cables using V-grooved cylindrical units: High performance cables

Some practical and theoretical aspects of a V-grooved cylindrical cable (high performance optical fiber cable) are now being developed in several countries. Design of cables is important, because bendings may cause distortions. In order to limit micro-bending losses in an optical fiber cable, it is possible to modify parameters relating to the fiber or the cable. Some of the possibilities are: to decrease the core diameter in order to decrease the attenuation coefficient; to increase the diameter of the cladding so as to increase the tension above which micro-bendings occur; to increase the continuous bending radius due to cabling; to decrease the effects of roughness (μ); to integrate the effects of roughness as much as possible by decreasing the Young modulus of the coating and of the cable material and by increasing the cladding thickness; and to suppress the tension T of the fiber in the cable. The cabling element is made of a V-grooved cylindrical core, in which the fiber with an outside diameter d_e (outside diameter or primary coating) are laid without tension, with a slight excess length. The slots with a depth h are helical or alternated helical, providing the possibility of additional excess length, and the fiber can be “cabled” directly without stresses. A central strength member with a diameter Dp reinforces the cylindrical rod, ensuring the mechanical and thermal qualities.     

Determination of thermal residual strain in cabled optical fiber with high spatial resolution by Brillouin optical time-domain reflectometry

The thermal residual strain induced in the cabled optical fiber is a very important factor for evaluating the reliability of optical fiber cables. In order to determine the distributed thermal residual strain in cabled optical fiber, a measurement method based on Brillouin optical time-domain reflectometry (BOTDR) system is proposed in the article. Thermal characteristics of residual strain along cabled optical fibers are investigated theoretically and experimentally based on Brillouin frequency shift (BFS) detection. The thermal residual strain along the cabled fiber, if any, can be determined with a high spatial resolution that is equal to that of the BOTDR system and can be less than a few meters. A double-coated fiber in loose optical cable was used as the test cabled optical fiber, and the experimental results were in good agreement with those predicted from the theory. It has been found that the fiber residual strain increases linearly with decreasing temperature in the range from 50 to ?50 °C.     

雨滴碰击光缆后光纤应变相位调制分析

基于云动力学理论,分析了雨滴碰击光缆后径向应变导致光纤纤芯折射率及形状发生改变,使光纤内传输光相位受到调制的过程.建立了雨滴碰击光缆引起光纤内传输光相位调制的模型,获得了降雨强度与相位调制之间的关系.研制了雨滴碰击光缆相位调制实验室验证系统,对比了模拟降雨强度分别为3,5,7,10,15,18,22,30 mm/h时的实验测试与仿真结果,两者变化趋势一致,误差在9%以内.该模型可用于仿真获得不同降雨强度下雨滴碰击光缆引起的光相位调制,为进一步研究降雨对光纤振动传感系统性能的影响,优化光纤振动传感工程应用系统,提出可行的雨量补偿方案提供了理论参考.     

基于大功率超窄线宽单模光纤激光器的φ-光时域反射计光纤分布式传感系统

提出了一种基于大功率超窄线宽单模光纤激光器的φ-光时域反射计光纤分布式传感系统.传感光缆采用普通单模光纤制成的直径3 mm的细光缆,并埋设于室外.入侵者走在光缆上面或附近产生的压力(振动)导致光纤中瑞利散射光相位发生变化,由于干涉作用,光相位变化将引起光强度的变化,通过实时将当前时刻的φ-光时域反射计后向瑞利散射信号与其前一时刻(时间间隔0.1 s)的后向瑞利散射信号连续相减检测这种干涉效应来定位入侵位置.经适当的数据处理后,该传感系统定位精度可达到50 m(为目前报道的φ-光时域反射计传感系统最高定位精度),定位范围可达到14 km,信噪比约为12 dB,且灵敏度较高.该系统可望能广泛用于军事基地、国界、核设施及监狱等重要场所的安全防范.     

不同封装光纤低温测温性能研究

基于拉曼散射的分布式光纤温度传感器由于具有抗电磁干扰、耐高压、可连续测温等优点,在超导电缆及相关超导电力装置中具有潜在应用场景.在超导电缆低温运行环境中,常规光纤封装材料耐低温性能差,其收缩变形会降低光纤测温性能甚至破坏光纤结构.本文对低温下不同封装光纤测温性能展开研究,选择四种光纤样品,在77～287 K温度区间内对其进行了稳态和动态温度测量实验,分析了低温下不同封装材料、结构和厚度等因素对光纤测温性能的影响,给出了适用于液氮低温测温的光纤封装材料和结构,实验验证了聚烯烃紧套光纤在时间和空间上连续测温的可行性.     

Recent Progress of Wavelength Division Multiplexing Technology In Tera-bit/s Transoceanic Undersea Cable Systems

Transmission capacity for optical undersea cable systems is growing remarkably and a more than 500-fold increase has been achieved for commercial systems over the past 10 years. The first optical fiber cable in the Pacific Ocean went into service in 1989 and has a capacity of 280 Mbit/s per fiber pair. The emergence of an Erbium-doped fiber amplifier paved the way for a drastic capacity increase for these cables, and large capacity optical amplifier undersea cable systems with 5 Gbit/s per fiber pair were constructed worldwide in 1995-1996. Recent 10 Gbit/s-based wavelength division multiplexing (WDM) technologies together with new fibers and new amplifiers have allowed a further increase in capacity up to 160 Gbit/s, and these WDM systems will begin commercial service in both the Pacific Ocean and the Atlantic Ocean in 2000. Research interest is now being directed towards the development of undersea cable systems with a transmission capacity of 1 Tera-bit/s or more. This paper reviews the key technologies for next generation 160 Gbit/s optical undersea cable systems and recent progress towards Tera-bit/s systems. Dispersion managed soliton transmission for future higher bit rate WDM is also discussed.     

日本光纤光缆产业技术创新及其启示

在回顾日本光纤光缆产业技术创新过程的基础上,对比中国光纤光缆产业的发展过程,并分别总结为"顺向"和"逆向"过程。最后,论文分析了导致不同过程的原因。     

基于分布式光纤Bragg光栅传感技术的光缆卷盘静态压力研究

基于对光缆卷盘缆层静态压力分布的理论分析, 建立了光缆缠绕体系中的受力理论模型. 研究表明, 随着缠绕层数的增加, 卷盘各层光缆所受压强先快速增大而后变化平缓. 采用分布式光纤Bragg光栅(FBG)对光缆绕线装置上缆层的静态压力进行了实时传感, 理论上给出了FBG的中心波长偏移量与体系压强的定量关系, 实验上发现各层FBG的中心波长随着光缆卷盘缠绕层数的增加先较快速变化而后趋于平缓, 理论模拟和实验测量结果符合得很好. 该技术解决了光缆绕线过程中无法对缆层所受压力进行实时监测的难题.     

Performance Analysis for Downstream Next Generation Converged WSN-PON ODN Network Incorporating Diverse Phase Delay

In this article, a cluster-based WSN convergence with passive optical network (PON) as optical distributed network (ODN) has been proposed, where sensed information of WSN is transferred over fiber cable to enhance the transmission range. The proposed integrated WSN-PON network has been investigated at different fiber lengths incorporating diverse phase delays to WSN data. The performance of the proposed scheme is reported in terms of optical spectrum, SNR, and BER. The outcomes prove fruitful convergence of WSN-PON ODN and serve as a guideline to develop such a converged network.     

Origin of temperature dependence of microbending attenuation in fiber optic cables

Abstract

Temperature-induced changes in the attenuation of multimode optical fiber cables are shown to be caused by mismatch between the thermal expansion coefficients of the fiber and the cabling materials. A quantitative theoretical model of low temperature loss, based on the formation of fiber microbends by microvariations in the jacket concentricity, is described. This model applies to tightly jacketed, soft buffered cable designs. An equation relating the low temperature optical attenuation to cable parameters is derived using this model. Good agreement is obtained between this theoretical prediction and experimental results. The theoretical model is used to compare the effectiveness of different cable designs on reducing excess loss at low temperature.     

Optical amplification of Eu(TTA)3Phen solution-filled hollow optical fiber

A liquid core optical fiber (LCOF) composed of hollow fiber and a solution of Eu(TTA)(3)Phen (TTA=2-thenoyltrifluoroacetone, Phen=1, 10-phenanthroline) in dimethyl sulfoxide (DMSO) has been fabricated, in which the concentration of Eu(TTA)(3)Phen in DMSO is 0.8 wt.%, the core diameter of the LCOF is 10 μm, and the fiber length is 8.1 cm. By the end pumping with a diode-pumped solid-state laser at 355 nm, a small optical signal at 613 nm was amplified with a gain of 8.2 dB at a pump power of 203 mW. Based on this experimental result, a liquid core optical fiber amplifier can be realized by the LCOF, which has wide potential applications in many optical devices.     

白光干涉偏振模耦合分布式光纤传感器分析

分布式光纤传感器能够测量沿光纤长度上连续分布的外界量。用保偏光纤作为传感光纤的分布式光纤传感器,被测外界量引起保偏光纤中传播的两正交偏振模的相互耦合。用迈克尔逊干涉仪两臂光程差来补偿两个偏振模的光程差的方法探测传感信号。为了设计白光干涉偏振模耦合分布式传感器,根据统计光学原理分析了传感器的互相干特性。在此基础上分析了传感器的空间分辨力、光纤耦合点分辨力、最大传感光纤长度。波长1310nm、谱宽36nm的超辐射发光二极管(SLD)作光源．用色散参量为600ps／km,拍长3mm的保偏光纤的分布传感器空间分辨力和光纤耦合点分辨力分别为6cm和3mm。     

采用光纤光栅级联结构实现光纤延迟线

在使用光纤光栅实现皮秒级别时延的基础上,提出一种光纤光栅与单模光纤相结合的微秒级别级联结构,该结构可以实现中心波长1 550～1 553 nm范围内,间距为1 nm的窄波长反射型时延线,共1, 1.5, 2和2.5μs四种不同的时延。将单波长反射的啁啾布拉格光纤光栅与103 m单模光纤连接构成延迟单元,再利用光环形器将4个延迟单元级联并使用内半径为3 cm的光纤绕线盘,将四种延时单元的传输光纤进行整合。借助光纤光栅的反射镜作用,控制不同波长光信号通过不同的传输距离,从而达到时延目的。本文通过对啁啾布拉格光纤光栅的反射谱进行仿真分析,发现相邻反射谱的旁瓣会出现交叠现象,因此使用六个切趾函数对旁瓣滤除。结果显示：不同切趾函数的滤除效果也不同,能够完全滤除旁瓣并且对反射谱包络影响最小的是柯西切趾函数,经柯西切趾后能使不同波长光信号在对应中心波长1 nm范围内反射率达到1,而其他位置均为0。由于使用光纤绕线盘整合延迟单元传输光纤会产生一定损耗,因此对弯曲损耗进行仿真分析,结果表明：弯曲半径相同时,损耗与工作波长成正比;工作波长相同时,弯曲损耗与弯曲半径成反比。当弯曲半径大于2.9 cm时,弯曲...     

入射偏振对有线电视光发射机受激布面渊散射抑制性能的影响

受激布里渊散射 (SBS)的抑制性能是光纤调幅有线电视外调制发射机的关键指标之一。从理论上分析了入射偏振分别为TE与TM模时 ,对发射机受激布里渊散射抑制性能的影响。分析计算显示 :入射光偏振态模式为TE模最佳。还对入射偏振态偏离TE模的情形进行了分析 ,表明为保证发射机对受激布里渊散射抑制性能 ,入射光偏离TE模的角度应小于 10°。