Study On Optical Time-domain Reflectometry Based On Pulse Chaotic Signal

With the increasing requirement of transmission rate and reliability of information in modern society, optical fiber has become one of the most important communication medium. And the measurement of transmission characteristic and fault location of fiber is playing a key role in the process of manufacture, construction, maintenance and repair. Optical time-domain reflectometry(OTDR) is the most widely used fiber measurement equipment, which can obtain attenuation information and fault location non-destructively. But there is a trade-off between the spatial resolution and dynamic range. Taking advantage of autocorrelation feature of chaotic signal and the pseudorandom code correlation OTDR, some researchers proposed chaos OTDR which overcome the shortcoming of the traditional OTDR. Although this method realizes the distance-independent spatial resolution, it can only locate faults infiber. Attenuation information is lost due to the feature of the probe signalAiming at the problems above and improve the original chaos OTDR, we designed an optical reflectometry system based on pulse chaotic signal combining the single pulse and chaos OTDR. Through this system, we can obtain attenuation information and keep the distance-independent high precision at the same time. This technique makes the function more comprehensive, increasing the measurement efficiency, and makes a progress of the conversion of the research techniques to the actual application.Detail works are summarized below:1. We introduce the traditional OTDR and the improved methods, and analyze and compare them.2. Based on the research basis of our group, we propose and determine the implementation scheme of improvement, which can realize fiber attenuation measurement.3. We analyze the measurement principle theoretical. After that, we measure different objects experimentally, and analyze the influence of different measurement parameters. The optimum scheme of the original measurement results is proposed. This method not only overcomes the trade-off of the traditional OTDR, but improves the original chaos OTDR. The spatial resolution of this experimental system is 0.6m, due to the 200 MHz bandwidth of the APDs.