【作者】 张一帆；

【导师】 董毅；

【作者基本信息】 上海交通大学 ， 通信与信息系统， 2009， 硕士

【摘要】 光时域反射计(OTDR)是表征光纤传输特性的测量仪器,可测量整个光纤链路的衰减并提供与长度有关的衰减细节,同时能探测、定位和测量光纤链路上的事件,如:接头损耗、尾端反射等。在实际工程应用中,用于电信长距离的光纤通信系统的安装与维护,并能在单端非破坏性地迅速准确地确定光纤中断点的位置。本文介绍了OTDR的发展历史与研究现状,分析了其工作原理和主要技术指标。OTDR的技术指标最终都可以归结为动态范围的提高和对微弱信号的检测能力。可以通过取样积分、相干OTDR、脉冲编码等方式提高OTDR的动态范围。本次设计实现了一种基于嵌入式系统的OTDR,它在硬件上具有噪声小、AD采样率高、取样精度大的特点,分别提高了动态范围、距离分辨率与损耗值分辨率;在软件上借助高性能的ARM处理器与FPGA控制系统实现了数据的高速采集和复杂的数字处理,从软件的角度进一步提升了动态范围和距离分辨率。经实验得出,该OTDR的动态范围达到了国内外的先进水平,其设计优势与局限性都为以后的版本提供了重要的改进思路,也为此类移动手持OTDR的产品化提供了有价值的技术参考。通过将该OTDR应用于无源光网络(PON),验证了用波形对比法定位和测量PON支路事件的方法,同时对OTDR的动态范围等技术指标以及波形比较等功能提出了更高的要求与更新的挑战。更多还原

【Abstract】 Optical time-domain reflectometry (OTDR) is an instrument to measure the transmission characteristics of fiber-link. It not only can measure the attenuation and report its detail with respect to distance along the fiber-link but also can monitor, locate and quantify any kind of events along the fiber such as slice loss, end point reflection and so on. In practical engineering application, the OTDR can be used in the installation and maintenance work in the long-haul fiber-optic communication system. It could accurately and rapidly locate the broken point along the fiber from one end without breaking the fiber.This paper introduces the history of development of OTDR and its status quo of research, analyzes the working principle and main technical specifications of OTDR. These technical specifications boil down to the improvement of dynamic range of OTDR and its capability of detecting weak signal as well. The dynamic range increase of OTDR could be achieved by coherent OTDR, co-related OTDR, sampling integration, pulse coding and so on.In this design we implement a new type of OTDR based on the embedded system. The hardware of this OTDR bears the strengths of low noise, high AD sample rate and high sample resolution, which promotes the dynamic range, distance resolution and loss value resolution of OTDR respectively; On the other hand, with the help of high performance device such as ARM processor and FPGA, we implement and high-rate data sampling and complicated digital processing, which improve the dynamic range and distance resolution of OTDR on a software bases. As shown by the experiments, the OTDR could boast itself among the advanced level in terms of dynamic range both at home and abroad. The achievement, strength in design and limits of this OTDR not only provide the methodology for improving in later version of development, but also offer the valuable technical reference for the manufacture of such kind of hand-held OTDR product.This OTDR is also put into use in the surveillance of PON architecture, which verifies the method of waveform comparison in the locating of fault events along the branches in PON. The experimental results also set higher requirements for the technical specifications and new function of OTDR such as dynamic range and waveform comparison. The OTDR is faced with more challenges in such kind of application.更多还原