Research Of Optical Network Monitoring System Based On Φ-OTDR And 2D Optical Coding

The power optical network is the foundation to ensure the stable operation of the power grid,and the establishment of a reliable and controllable optical communication network is a strong support for the digital development of the power grid.At present,the management and fault finding of power optical networks rely heavily on manual work,using too long time and may cause error.There is an urgent need for a centralized monitoring technology,to automatically identify the physical topology of the optical link by using the built-in optical tag of the fiber,diagnose the link health status,and quickly and accurately locate the fault location on this basis,realize the optical digital management of optical networks.In this thesis,a centralized fault monitoring system for optical networks based on phase-sensitive optical time-domain reflection(Φ-OTDR)and two-dimensional optical coding technology is proposed.It is mainly aimed at the health monitoring of multiple optical fiber links starting from communication stations in point-to-point optical networks.In this system the Φ-OTDR is used in optical networks to detect vibration signals along optical cables to early warning the fault of the most important link.And by using the optical coding technology,the physical path and fault of all monitored links can be quickly identified.And the encoder’s ability to mark the position of the optical fiber is used to improve the accuracy of Φ-OTDR for the physical location of the fault.First of all,on the basis of investigating the content of domestic and foreign literature,the development status of multi-link fault monitoring technology applied to optical networks is studied,the advantages and disadvantages of various technologies are analyzed and summarized.According to the demand of link monitoring in power optic network,the combine the optical coding and Φ-OTDR to achieve centralized fault monitoring was deciding.Secondly,basing on the basic principle of grating reflection,the optical encoder is constructed by using a weak reflection grating string,through identifying the reflected signals from different encoders in the link,the acquisition of the network physical topology is realized.Based on the research of heterodyne Φ-OTDR principle and demodulation method,the restoration of vibration signal in optical fiber was completed.And in order to meet the requirements of centralized multi-link management,the multichannel optical switches are used with automatic routing algorithms to achieve the monitoring of multiple links and also maintain the fault response efficiency.The efficient integration of the two detection methods of the system is realized.Thirdly,aiming at the manual and mechanical mining events that may cause faults around the optical cable,the fault early warning method based on the identification of signal feature is studied.By studying the changes of detection information caused by common faults in optical fibers,a fault identification and location method was constructed.Combined with two optical path protection measures,an optical network fault monitoring algorithm for centralized management of multiple links is designed.Finally,a system test prototype was built.And he experiments show that the system can realize the monitoring of 10 km long optical link,and can identify up to eighteen encoders in one link when using six coding wavelengths,and the spatial resolution of optical coding identification reaches four meters,and proved that the system can quickly respond and locate the faults that happened in the fiber.The fault warning ability of the system was verified by carrying out simulated mining experiments at the field above the communication optical cable.The current engineering application of this research content is introduced,and the feasibility of practical application of the system is verified through experiments.