Abstract
We report on the development and implementation of an optical frequency-domain reflectometer (OFDR) sensing platform. OFDR allows to measure changes in strain and temperature using optical fibers with a length of several tens of meters with very high spatial resolution. We discuss the operation principles and challenges to implement an OFDR system using optical homodyne detection based on a dual-polarization 90° optical hybrid. Our setup exhibits polarization and phase diversity, fully automated data acquisition and data processing using a LabVIEW-based implemented software environment. Using an optical hybrid enables to discriminate phase, amplitude and polarization by interfering the Rayleigh scatter signal and a local oscillator with four 90° phase stepped interferences between the two signals. Without averaging and a fast acquisition time of 230 ms, our preliminary results show a spatial resolution of 5 cm and a temperature resolution of about 0.1 Kelvin on a 3 m-long fiber.
Highlights
Over the last decades the field of optical fiber sensing has grown immensely
We developed a short-range distributed optical fiber sensing platform based on optical frequency-domain reflectometry (OFDR) method for temperature and strain monitoring
We have designed and realized an integrated OFDR sensing platform, that contains all opto-electronic components in a compact enclosure
Summary
Over the last decades the field of optical fiber sensing has grown immensely. The application fields of the technology range from shape sensing, pipeline and electrical transmission line monitoring, structural health monitoring, or intrusion detection for perimeter security applications [1]. Unlike optical time-domain reflectometry (OTDR), optical frequency-domain reflectometry (OFDR) interrogates a sensing optical fiber in the frequency domain using a tunable continuous-wave (CW) laser, which enables high spatial resolutions while securing high signal-to-noise ratios. While one part of the light is sent into a sensing fiber, another part is used as an optical local oscillator to enable coherent detection. The spatial distribution of the reflected light along the fiber is obtained using both the Fourier and inverse Fourier transforms of the measured coherent Rayleigh backscattered signal
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