Research On Spatial Resolution And Dynamic Range Of A New Distributed Optical Fiber Sensing System

With the rapid advancement of communication technology,a large number of optical fibers have been deployed as communication media,making maintenance and detection of the fibers particularly important.Based on optical time domain reflectometry technology,this article improves the differential phase shift keying(DPSK)modulation and demodulation system and the spread spectrum system,and uses a new type of optical fiber ranging system to achieve monitoring point positioning.The parameters of the optical fiber ranging system are also improved.The main content of the paper is as follows:Firstly,this article introduces the background and application areas of optical time domain reflectometry(OTDR)technology,indicating that this technology not only plays an important role in the field of optical fiber communication,but is also widely used in boundary detection,fault diagnosis,and other areas.Based on OTDR technology,the related research on spatial resolution and dynamic range is expounded.Secondly,this article uses a new Mach-Zehnder interferometric structure and elaborates on the working principle of the new Mach-Zehnder interferometric structure demodulation in detail.The characteristics of the new Mach-Zehnder interferometric structure,such as high temperature stability,good robustness,and low requirements for the light source linewidth,are analyzed.To avoid the "electronic bottleneck" problem,a multiplier that operates in the optical domain is also used.Meanwhile,a distributed optical fiber ranging system is built based on the new Mach-Zehnder interferometric structure and the optical domain multiplier,and the feasibility of this optical fiber ranging system is verified.Next,the relevant theories of spatial resolution of OTDR are analyzed,and the arm length difference comparison method and the multiple sampling method are proposed respectively.By comparing the arm length differences of different lengths in the Mach-Zehnder interferometric structure,the conclusion is drawn that shortening the arm length difference can improve the spatial resolution of the system.In the multiple sampling method,the sampling points are increased N times in software,and the original sampling point spacing is reduced to achieve an improvement in spatial resolution.The multiple sampling method is further improved by constructing a fit to achieve error positioning of less than 0.2 m.Finally,the relevant theory of dynamic range of OTDR is analyzed,and three methods based on signal-to-noise ratio are proposed to improve the system’s dynamic range.By changing the system sequence length,the integration value can be increased,and the signal-to-noise ratio can be increased.By adding an optical fiber amplifier to increase the output power,the signal-to-noise ratio can be improved,and the dynamic range can be enhanced.In the wavelet denoising method,the final integration value is processed by wavelet denoising,and by setting a new threshold function,the useful signal is optimized to achieve the purpose of improving the system’s dynamic range.