Key Technologies Of Long Distance Distributed Optical Fiber Positioning System

Optical fiber sensing is a new type of safety monitoring technology which is safer,more reliable and can be applied on the large scale sensing field.As is well known,the Dual M-Z long-distance distributed optical fiber positioning technology is widely used in oil and gas pipelines,intelligent security and other fields.However,with the wide application of optical fiber sensing in different systems,it has been a gradually prominent contradiction between the performance indicators such as positioning accuracy and response speed and the increasingly stringent demands,which is shown as following:Firstly,the real-timing of positioning algorithm and the complexity of computation challenge the stability and reliability of the entire system.Secondly,Random polarization fading problem of the dual M-Z systems makes the inaccurate positioning accuracy.Then,regarding the above problems,this research will be conducted in the following three aspects:(1)Considering the characteristics of computer system in digital signal processing,a distributed optical fiber sensing localization method is proposed based on multi-mean period which fully considering the interaction and processing of data during system operation.Compared to traditional positioning algorithm,the proposed algorithm has been used to reduce the number of calculations of cross-correlation algorithm significantly and enhance the stability and reliability of the dual M-Z systems.(2)A real-time closed-loop feedback control system for the random polarization fading problem is proposed.Firstly,by timing modulation of light source,the disturbance is generated,and at the same time,the two-channel light intensity signals are used as the input of polarization feedback control system.Then,based on the optimization algorithm of polarization control,the four-channel output signals of piezoelectric ceramic generated by the electro-polarization controller are used to extrude optical fiber to realize the polarization state automatic regulation.Secondly,for the problem of fast optimization algorithm of the polarization control,a particle swarm optimization algorithm based on simulated annealing is used to realize fast optimization and polarization recovery control.Finally,the effectiveness and performances of the proposed method are validated and demonstrated with the actual testes.(3)A high-speed acquisition card based on PCI-Express interface is designed.Considering the problem of fast real-time acquisition of two-channel signals,improving the positioning accuracy of the system and solving the delay problem of the polarization controller,a high-speed acquisition card based on PCI-Express interface is designed by using the development technology of FPGA in which the front-level digital signal processing and the data operations with strict real-time requirements are customized to the self-made high-speed acquisition card.The relevant practical tests verify the stability and reliability of data transmission.The work of this article is helpful to improve the positioning accuracy and reliability of the long-distance positioning system based on dual M-Z optical fiber sensor in practical engineering application.It has certain technical reference values for the existing and future long-distance positioning systems.