The Long-Distance Distributed Optical Fiber Sensing System Based On The Novel Amplification/Receiving Method

The long-distance distributed optical fiber sensing(DOFS) systems have been widely used in the field of perimeter security, electric power facilities, pipelines, high-speed Rail structure safety and health monitoring, etc. Therefore, in order to extend the sensing distance, the valuable research works should be carried out, including signal amplification schemes and receiving technology.In this paper, the novel amplification and receiving technology is applied to the long-distance DOFS system. To improve the sensing performance of the phase-sensitive optical time-domain reflectometry(Φ-OTDR) and Brillouin optical time-domain analysis(B-OTDA) system, we respectively propose to use Brillouin amplification scheme and balanced detection technology, which is based on the DOFS sensing theory and performance index. Meanwhile, the theoretical simulation model and experimental design of the DOFS system have also been demonstrated. Also, we take participate in the research on commercialized DOFS system. Following work is carried out:(1) The DOFS technology and research is summarized, especially demonstrated the sensing mechanism of the Φ-OTDR and B-OTDA system in detail. The key factors influencing the performances of sensing system are analyzed theoretically. At the same time, the technical principles and application of traditional amplifying and receiving technologies are introduced.(2) We experimentally study a dual-sideband Brillouin optical time-domain analyzer(BOTDA) with balanced detection. 200km(8m spatial resolution, and 1.2 temperature accuracy) fiber-loop sensing system is achieved(half of the whole length is used for sensing), with only bi-directional first-order Raman amplification. Here, we investigate the impact of the optical source’s wavelength with regard to the given FBG on the system’s performance.(3) We propose a novel Φ-OTDR scheme with counter-pumping fiber Brillouin amplification(FBA). Compared with counter-pumping fiber Raman amplification(FRA) scheme, the FBA simulation model have also been established, and we research on the temperature characteristics of the FBA technology.(4) FBA significantly enhances the probe pulse signal, especially at the second half of the sensing fiber, with only 6.4dBm pump power. It is confirmed that its amplification efficiency is much higher than 28.0dBm counter-pumping fiber Raman amplification. High-sensitivity perturbation detection over 100km(10m spatial resolution) is experimentally demonstrated as an example. Meanwhile, we have completed the test on the artificial disturbance, temperature variation and the signal-to-noise ratio(SNR). In addition, the effect of pump frequency variation is studied, and the system shows reasonable robustness and flexible, which can be applied to partitioned domain amplification.(5) Assisted complete two sets of engineering prototypes, including the distributed optical fiber intrusion detection system and distributed temperature measurement system, which is based on single-mode fiber(SMF) and integrated. Also, we solve practical problems, including mainframe layout, external interface, connection, etc. At present, the distributed intrusion monitoring system has been successfully applied to submarine cable safety monitoring project.