A distributed Brillouin dam health monitoring scheme based on differential pulse pairs

Abstract

To meet the high-precision positioning requirements of dam health monitoring,this paper designs a high spatial resolution distributed Brillouin dam health monitoring scheme based on DPP-BOTDA (Differential Pulse Pair Brillouin Optical Time Domain Analysis) technology.Due to the large pulse width and strong pulse energy of the two differential pulses used in the Brillouin system, the high-precision measurement of Brillouin frequency shift can be achieved; Moreover, the difference in pulse width between the differential pulse pair is small, which can achieve high spatial resolution and meet the high-precision positioning and measurement requirements for dam health monitoring.The rise and fall time of the pulse signals is a key factor affecting the spatial resolution of DPP-BOTDA systems. To achieve centimeter level spatial resolution, this paper designs a SOA (semiconductor optical amplifiers) narrow pulse driving circuit that can generate pulse signals with rise and fall times less than 1 ns (ps level pulse edge). An experimental setup for the DPP-BOTDA system is built. The SOA narrow pulse driving circuit mentioned above is used to generate pulse signals with pulse widths of 48ns and 50ns, respectively, for differential Brillouin tests. By analyzing the spatial resolution test curve of the system with the differential pulse signals demodulation, it can be concluded that the system can achieve a spatial resolution of 0.2m. It meets the high spatial resolution requirements for dam health monitoring and is of great significance in the field of distributed Brillouin fiber optic sensing applications.