A novel in-service measurement technique using the same wavelength band as SCM signals

This paper proposes a new technique for measuring in-service optical fibers, that uses an optical time domain reflectometer (OTDR). The feature of the proposed technique is that the OTDR light is in the same wavelength band as the video signal, which is distributed by using the subcarrier multiplexing (SCM) technique. In a 40-channel SCM system operating at a signal wavelength of 1.558 /spl mu/m, we show that the required video quality can be maintained, by using the proposed OTDR operating in the 1.55 /spl mu/m band, even though the measured fiber is in service and the OTDR light enters an optical receiver. Moreover, we clarify the conditions for undertaking measurements, without the need for optical filters designed to prevent OTDR light from degrading the SCM signal quality.     

Optical time domain reflectometry in optical transmission linescontaining in-line Er-doped fiber amplifiers

Optical time domain reflectometry (OTDR) in an optical transmission line containing in-line Er-doped fiber amplifiers is investigated. The proposed Er-doped fiber amplifiers are based on optical circulators, which support both OTDR and digital signal transmission. The measurable limit of OTDR fault location in optical transmission lines containing in-line amplifiers is discussed. Fault location and 1.8-Gb/s digital signal transmission are demonstrated in a 316.9 km, optical transmission line constructed with three in-line Er-doped fiber amplifiers     

基于双向OTDR测试的光传输网实时监测系统

基于现有的光信号处理技术、网络技术以及OTDR等设备设计并实现光传输网实时监测系统,提出基于双向OTDR测试来解决OTDR在长距离测量光缆线路时动态范围受限的问题,同时结合采用GIS等技术开发的光缆线路管理系统(FMMIS),进行对光传输网络的实时监测,实现了光纤中断故障的自动精确定位。     

光缆实时监测系统

提出了一种新型光缆实时监测系统的设计方案，系统通过光耦合器对每根光纤的光信号取样，然后对其光功率进行测试，将测试结果送到中央控制器进行计算，分析和处理，显示出测量数据，并根据处理结果控制光开关进行切换，再通过波分复用器（WDM）使故障光纤接入光时域反射计（OTDR）进行上下测试。     

OTDR in optical transmission systems using Er-doped fiber amplifiers containing optical circulators

Fault location in optical amplifier transmission systems is described. Optical time-domain reflectometry (OTDR) cannot be used for an optical transmission line containing traditional Er-doped fiber amplifiers (EDFAs) because they contain optical isolators. The authors propose an OTDR scheme that uses new EDFAs containing optical circulators and return transmission lines. The new EDFAs support both OTDR and digital signal transmission. A 280.9 km transmission line containing three of the proposed EDFAs was constructed and tested. Experimental results demonstrated the feasibility of OTDR fault location and 1.8-Gb/s digital signal transmission.<>     

High-accurate fault location technology using FSK-ASK probebackscattering reflectometry in optical amplifier submarine transmissionsystems

This paper proposes a new modulation format for optical time domain reflectometry (OTDR) to eliminate optical surge and improve OTDR performance in optical amplifier submarine transmission systems. The modulation format, FSK-ASK, uses a short high-power probe pulse and a long dummy pulse. Thanks to the slow gain dynamics of erbium-doped fiber amplifiers, both pulses experience an identical gain, equal to the loss of a span, so that the probe pulse maintains its high power and does not develop into an optical surge. Fault location experiments verify a theoretical prediction that FSK-ASK improves the signal-to-noise ratio (SNR) of OTDR by an amount as large as the power ratio of the probe to dummy signal. They also confirm the elimination of the optical surge caused by conventional OTDR using a solitary probe pulse. An FSK-ASK OTDR is applied in a commercial submarine amplifier transmission system which has a total transmission length of 890 km and a repeater spacing of 90 km. These field trial results show that subtle fiber anomalies can be located, with a spatial resolution of 1 km, along the entire length of the amplifier transmission system from a terminal end     

一种基于相位敏感光时域反射计的多参量振动传感器

提出了一种基于数字相干检测和维纳滤波技术的相位敏感光时域反射计(φ-OTDR)。在该技术中,实时解调出了沿光纤链路散射回的瑞利信号电场的振幅和相位。通过分析解调出的振幅和相位,检测到了位于3.5km传感光纤上的一个由压电陶瓷(PZT)所产生的正弦振动信号的位置、频率和强度。应用维纳滤波降低了由激光器的相位噪声和探测器加性噪声引起的相位波动。系统的空间分辨率为5m。     

一种用于光时域反射仪的1550nm半导体激光器

光时域反射仪(OTDR)是通信链路中光纤特性测试的专用仪器,半导体激光器是OTDR的关键元器件,激光器的性能直接影响OTDR的测试距离、测试精度等。为适应OTDR的应用需求,提出并研制了一种非对称分别限制(SCH)激光器,SCH结构可有效提高激光器的输出功率和斜率效率。同时,采用应变多量子阱结构来提高器件的温度特性。研制的1 550nm±20nm工作波长的激光器,其单模尾纤输出功率大于等于60mW(工作电流300mA,25℃),激光器上升/下降时间小于1ns,完全满足OTDR长距离、高精度测试的使用要求。     

Novel OTDR Technique for Measuring Relative-Index Differences of Fiber Links

A novel technique is proposed for measuring the relative-index difference of the fiber links using an optical time-domain reflectometer (OTDR). The material dispersion of the fiber links can be estimated by using this method. Moreover, the chromatic dispersion distribution of a fiber link is successfully estimated by combining this technique with the conventional OTDR technique     

Development of a coherent OTDR instrument

Optical time domain reflectometry (OTDR) is a commonly used technique for characterization and fault location of optical fiber transmission systems. It involves measuring the fraction of a probe pulse that is scattered back (by Rayleigh scattering) from a silica fiber. Because of the very small levels of backscatter in single-mode fiber at long wavelengths, very sensitive optical detection is necessary to achieve adequate range performance. This paper gives the principles of operation and performance of a coherent OTDR system designed for use at 1.3 μm and its realization as a robust field-portable instrument with a specified performance of better than 24-dB one-way range, and 0.2-dB fault loss resolution. Coherent detection gives ultimate receiver sensitivity and also reduces the dynamic range requirements of the electronic signal processing. To realize these advantages, a novel technique is used to provide the necessary highly coherent source from a semiconductor laser. Sophisticated Signal processing techniques are employed both pre- and post-detection to integrate the signal out of the noise and also to reduce coherent fading effects. The various components of the system and their development into a robust instrument are described, and the performance of the system over long lengths of fiber both in the laboratory and more importantly on installed transmission links is presented in detail, showing achieved performance considerably better than this specified minimum.     

OTDR系统波形的分析及其在光纤测量中的应用

本文利用瑞利散射原理分析了脉冲信号和脉宽大于、小于回波时间的方波信号的回波信号波形,并利用数值模拟得到了其理论波形图。根据原理自主搭建了一套光纤光时域反射仪（Optic Time Domain Reflectometer,简称OTDR）,用通信中通用的1550nm激光波长对样品光纤进行了实际测量,得到了与理论模拟完全一致的实测波形。通过对实测波形进行降噪处理得到了高精度的长度测量值和损耗测量值。长度测量的相对误差仅为0.0085%,与直接测量值比较,光纤传输损耗的相对误差为0.086%,理论与实验表明该OTDR系统完全可以与工程用的OTDR系统相媲美,在工程技术和教学研究中具有一定的应用前景。     

相位敏感OTDR系统的信号解调方法

提出了一种改进的关于相位敏感光时域反射计(OTDR)系统的信号解调方法.从理论上阐述了该方法的原理,分析了该方法中关键参数(平均次数、滑动窗口和相减间隔)的取值对相位敏感OTDR系统信号处理结果的影响,并且总结了它们取值的指导依据。与常规的数字平均方法对比,利用该方法进行数据处理,有效地解调出扰动信号,进一步说明该方法的可行性.结果表明,该方法根据信号的波动特征将原始数据进行分组,提高了各组数据的相关性,从而明显改善了系统的信噪比,对长距离相位敏感OTDR系统性能的优化有一定的指导意义.     

拉曼散射分布式光纤温度传感器的设计

文章论述了基于反斯托克斯／斯托克斯比值的分布式光纤温度传感器系统，对其信号处理技术进行了全面而深入的研究。采用光时域后向散射技术来获取温度信息，并用时域信号数字积累平均方法来提高系统的信噪比，据此建立了分布式温度传感器。     

基于VMD与SSA的OTDR信号去噪算法

为对光时域反射计(Optical Time Domain Reflectometer, OTDR)数据进行去噪处理,提出了一种基于变分模态分解(Variational Mode Decomposition, VMD)与奇异谱分析(Singular Spectrum Analysis, SSA)的去噪算法。首先,对OTDR数据进行VMD分解;然后根据相关系数准则判定有效分量,并采用SSA对与原信号相关系数较小的分量进行处理;再对所有分量求和,得到重构后的信号,从而实现数据信噪比的提高。经实验验证,该算法的去噪效果良好,容易实现,具有较大的实用价值。     

基于LFM-OTDR的超长跨距光纤电力通信链路监测

为了降低电力通信系统中白噪声和随机多径噪声,提出了2种基于线性调频-光时域反射仪(LFM-0TDR)技术的监测方案,即单频LFM-0TDR方案和频分复用LFM-0TDR(FDM-LFM-0TDR)方案.该监测方案采用LFM光脉冲信号作为探测信号,利用分数阶傅里叶变换将后向散射回来的探测信号变换到分数阶傅里叶域进行信号处...     

OLT PON端口内置OTDR技术分析

摘要：伴随着“宽带中国”战略的推进,FTTx大规模部署,同时光纤故障检测需求越来越多,需要一种以较低成本实现PON故障检测,提高运维效率的解决方案。因此,研究了OLT PON端口内置OTDR 技术,分析比较了不同波长方案的实现和成本,重点提出了基于PON 端口内置OTDR 的PON 系统架构,给出PON 端口内置OTDR 技术的测试性能要求以及限制其对设备、通信业务影响的要求,从而使PON端口内置OTDR 能够满足运营商的PON运营检测需求,提高运维效率。     

Tunable OTDR Based on Direct Modulation of Self-Injection-Locked RSOA for In-Service Monitoring of WDM-PON

We propose a tunable optical time-domain reflectometer (OTDR) for in-service monitoring of wavelength- division- multiplexing passive optical networks (WDM-PONs). The proposed method uses a reflective semiconductor optical amplifier, which is self-injection-locked by a tunable fiber Bragg grating. The proposed tunable OTDR has a tuning range of 30 nm and a resolution of 50 m. The performance of the proposed scheme is experimentally evaluated to demonstrate the in-service monitoring of WDM-PON.     

背向散射曲线上出现幻峰的理论分析

用OTDR测试光纤线路时，其背向瑞利散射信号曲线上常出现幻峰。对幻峰产生的原因进行了定量的分析并简述了幻峰对光纤线路测试的影响以及幻峰的辨别和消除。     

OTDR在光纤测量中的应用

介绍ＯＴＤＲ工作原理及主要性能参数;详细说明ＯＴＤＲ在光纤测量中参数的设置及测量方法;结合工作实践提出了ＯＴＤＲ在实际光纤测量中的几点经验和技巧。     

长距离高精度的线性调频光时域反射仪

为了对西藏人烟稀少地区和单跨段传输距离很长的光纤链路进行检测,文章提出一种用于提高线性调频(LFM)光时域反射仪(OTDR)空间分辨率和测量距离的方法。该方法通过产生一个调频范围为200 MHz、脉冲宽度为20μs的强度调制模拟LFM信号来实现高的空间分辨率和大的探测距离。使用该方法在西藏地区的实际光纤传输链路中进行了实验测试,实验结果表明,该方法能够在长度为240 km的光纤链路上实现0.000 53 km的空间分辨率,与相同测量参数的单脉冲OTDR相比,动态范围提高了8.5 dB。