In this work, a high-sensitivity distributed lateral pressure sensor based on Brillouin Optical Time-Domain Reflectometry (BOTDR) technique is proposed to enhance the pressure sensitivity using a double-coated Single-Mode Fiber (SMF). Firstly, a pressure-induced strain model is developed to analyze the enhancement mechanism of pressure sensitivity by Brillouin Frequency Shift (BFS). With increasing of outer coating radius, or with decreasing of the Young’s modulus and Poisson’s ratio of outer coating, the lateral pressure sensitivity increases. By using a double-coated SMF whose outer coating radius is 1500 μm, a high sensitivity of -3.51 MHz/MPa in the range of 0-30 MPa is achieved, which is about five times higher than that of single-coated SMF. At a spatial resolution of 1.5 m, the maximum measurement error of the proposed pressure sensing system is less than 0.09 MPa.
Due to its high sensitivity and fast measurement, the phase-sensitive optical time-domain reflectometer (φ-OTDR) is a good candidate for distributed dynamic strain sensing and has been widely used in intrusion monitoring, geophysical exploration, and other fields. In the case of frequency scan-based φ-OTDR, the phase change is expressed as a shift in the intensity distribution. The correlation between the reference and measured spectra is used for relative strain demodulation, which imposes a limitation on the absolute strain demodulation for continuous measurements. The Brillouin optical time domain analysis (BOTDA) fortunately enables the demodulation of the absolute strain in just one measurement. A combination of φ-OTDR and BOTDA is proposed and demonstrated in this work by using the same set of frequency-scanned optical pulses, and also introducing a frequency-agile technique for fast measurements. Measurements of 9.9 Hz vibrations were made at two different absolute strains (296.7 με and 554.8 με) with a strain range of 500 nε, made possible by integrating Rayleigh and Brillouin information. The submicron strain vibrations were demonstrated by φ-OTDR signals with a high sensitivity of 6.8 nε, while the absolute strains were measured by BOTDA signals with an accuracy of 5.4 με. Thus, the proposed sensor allows dynamic absolute strain measurements with high sensitivity, thus opening the door to new possibilities yet to be explored.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.