Research On Fiber Link In-service Mornitoring Method With Large Dynamic Rang

Fiber is the main carrier of wired communication.With the development of 5G technology,fiber will play a more and more important role in the network.In communication process,the accidents caused by the interruption of transmission will produce enormous social impact and economic losses.Therefore,the early warning and location of accidental damage that may occur to the fiber is very important.One of the key technologies to solve the problem is the in-service monitoring of optical fiber.In the optical fiber in-service monitoring scheme,the monitoring signal and service signal transmit through the optical fiber at the same time using the same wavelength,which doesn't occupy additional resource of wavelength.The monitoring scheme need to find and position the bending,fracture of the fiber and ensure the transmission quality of service signal at the same time.But at present,the existing in-service monitoring program has two main problems,one of which is the dynamic range is not large enough to cover long fiber cross section influenced by the service signal.Besides,the monitoring signal will negatively affect the time delay and transmission quality of service signal.This paper focuses on the research on optical fiber link in-service monitoring methods and related technologies.The main research work is as follows:1.According to the basic requirements of fiber monitoring,we put forward a bidirectional optical fiber in-service monitoring scheme based on IB_OTDR.In the scheme,the DC monitoring signal is added to the service and can be divided with each other using filters.The bidirectional IB_OTDR launches monitoring signal in turn at two sides of the fiber,which can double the distance of optical fiber to monitor.This scheme can achieve a large dynamic range and high spatial resolution.It also ensures the transmission quality of service signal better.2.According to the scheme of bidirectional IB_TDR in-service monitoring system,a DSP algorithm is designed.The algorithm includes four sub modules of average module,filtering,subtraction and event process.Aiming at the problem that event monitoring distance is limited,we put forward an event process method based on“correlation enhancement of local data".The simulation and experiment results show that the DSP process method can improve monitoring distance of events remarkably.3.Optical fiber link in-service monitoring simulation system is established using Matlab programming.The influences that parameters have on the scheme performance are simulated and analyzed.The transmission quality of service signal is simulated using VPI.The feasibility of optical fiber in-service monitoring scheme is verified.The simulation results show that the dynamic range of IB_OTDR optical fiber in-service monitoring scheme can realize a dynamic range of 36dB by bidirectional monitoring and a spatial resolution of 20m under typical conditions.4.The off-line experiment platform of the IB_OTDR fiber link in-service monitoring system is established.In the off-line experiment platform,the influences that key parameters have on the scheme performance are experimented and analyzed.The transmission quality of service signal is analyzed according to the experiment results.The experiment results show that the proposed bidirectional in-service monitoring scheme can reach a dynamic range of 3 6dB and a spacial resolution of 20m under the existing condition.