Research On Some Problems Of The BOTDR-based Optical Fiber Sensing Technology

Brillouin Optical Time Domain Reflectometry (BOTDR) is a rapidly developing and vigorous optical fiber sensing technology, which can be used to obtain the distributed temperature and strain informations, and thus it has a broad application prospect. Since its inception, many researchers have achieved remarkable achievements in both basic theory and practical applications, and it has been a research focus of optical fiber sensing field.In this dissertation, some problems of the BOTDR are investigated and explored. The sensing mechanism of BOTDR is described, and the characteristics of the corresponding electrical signal in the spontaneous Brillouin signal detection are detailed. We also explore the impact of the averaging methods on the power curve. The performance parameters of the BOTDR system, such as spatical resolution, measurement accuracy of Brillouin frequency shift (BFS) and dynamic range, are analyzed. By introducing the concept of energy weights curve, the formula that calculating the rising edge of the BFS curve of DFT-BTDR system is studied. The influence of two pulsed-light-modulation-methods on the power spectrum in BOTDR dection is discussed, and relationship between the pulsed light’s extinction ratio and the signal-to-noise ratio(SNR) of BOTDR system has been verified experimentally. We also proposed a wavelength-scanning BOTDR, which combines the advantages of optical frequency-difference scanning method and the electrical frequency scanning method. The feasibility of the proposed method is demonstrated experimentally.