Introduction
The fiber optical cable monitoring system monitors the fiber optical cable and then judges whether the optical cable is in normal operation; when the abnormal situation occurs, alarms will be issued and corresponding tests will be sent. In addition, through the judgment of fault data the position where fault occurred can be accurately located, the faulty equipment and the reason causing the fault can be quickly ascertained. 

The implementation process of the optical cable monitoring system is divided into three parts: information collection, summary and analysis, evaluation and diagnosis of equipment operation. Information is collected so that workers can know the status of monitoring status well.

The function of data collection will be lost if the collected data is not summarized and analyzed, the problems reflected by the data will not be found, and the internal rules will not be revealed, making it difficult to implement monitoring.

Evaluate and diagnose equipment performance. Since monitoring is the most basic maintenance activity, the ultimate goal of maintenance is to be able to evaluate and diagnose.

Structure
The optical cable monitoring system is mainly composed of monitoring center, RTU remote testing station and operation terminal. The remote monitoring station mainly includes optical time domain reflectometer OTDR, optical power monitoring OPM unit, optical switch OSW, etc. It is divided into monitoring unit and testing unit. The former mainly monitors the cable information, the latter mainly test the running status of cable. The Monitoring center is located in the control center of optical cable monitoring system, including monitoring network management systems and servers. The main function is to send test and switching commands to the optical time domain reflectometer and optical switch according to the received alarm from the tube power monitoring unit, and to accurately analyze and determine the fault point according to the feedback test results.

The operation terminal is the user's operation terminal for the whole system, including the PC terminal and corresponding software, which mainly provides convenient conditions for the user to maintain the line and find the fault point.

Monitoring Ways
OTDR positioning monitoring, optical power monitoring, and combination of OTDR positioning monitoring and optical power monitoring

OTDR positioning monitoring is through online monitoring and backup fiber monitoring. Online monitoring monitors the optical fibers.The WDM is split by the light waves, then the light from the OTDR is transmitted to the service fiber.The wavelength of the test light is transmitted to the unused port of the service fiber. For example, an optical fiber has a 1450nm port to transmit the service optical fiber data. The WDM can be multiplexed by 1300nm OTDR at the transmitter end. In this way, the optical fiber can be loaded with two light waves of different wavelengths at the same time and separated by WDM at the receiver end.

The principle of backup fiber monitoring is that the fiber pigtail is drawn from the OSW and connected to the ODF, where it is connected to the backup fiber. This kind of optical cable monitoring system only monitors the standby optical fibers, so the system price is relatively low.

Optical power monitoring is carried out using two monitoring stations. Set up an independent light source in the center of these two stations, set the detection mode of optical power in the detection station, and set the alarm threshold. When the optical power consumption exceeds the alarm threshold, an alarm signal will be generated to motivate the startup test and then determine the fault information.

The combination of the two refers to OTDR and optical power, so that the complementary advantages of the two can be used to operate the monitoring system and complete the information transmission function.

Conclusion
The rapid development of optical network makes it hard for the maintenance and labor now, it challenges the traditional maintenance and repair. Therefore, it is necessary to adopt the latest science and technology to manage the information transmission of monitoring system, observe the optical fiber in a dynamic way, find out the failure time and fault location accurately, and ensure the effective transmission of communication information.