Optical fiber Brillouin sensing at kHz rates using low-bandwidth electronics
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Author
Chin, Sanghoon
Stauffer, Yves
Soto, Marcelo A.
DOI
https://doi.org/10.1109/JSEN.2025.3546790
Abstract
This paper proposes an optical fiber sensing technique for dynamic monitoring of physical parameters such as temperature, strain and acoustic vibrations. The proposed dynamic sensor is based on amplified spontaneous Brillouin scattering and achieves kHz-level interrogation rates by using time-division fast Fourier transform on a down-converted Brillouin signal at an intermediate frequency. Unlike classical Brillouin sensors, this scheme provides pointwise monitoring, making use of the mutual interference between amplified spontaneous Brillouin scattering generated along a sensing optical fiber and an optical local oscillator taken from the pump source. The typical ∼10 GHz beating frequency in single-mode optical fibers is scaled down by a factor of 100 using a microwave frequency divider, enabling the use of low-frequency electronics around 100 MHz. The method measures the entire Brillouin spectrum accurately using a low-bandwidth analog-to-digital converter, eliminating the need for optical frequency scanning. Compared to other point fiber sensing schemes, like fiber Bragg gratings, this approach does not require optical frequency scanning components (e.g. scanning lasers or filters at the receiver) or special treatment of the sensing fiber. In addition, the sensor sensitivity can be adjusted by changing the sensing fiber length or by simply modifying the temporal windows of the Fourier transform. Experimental results validate the method, demonstrating dynamic sensing at 1 kHz refresh rate along a 78 m-long sensing fiber, achieving a frequency uncertainty of 0.66 kHz, corresponding to temperature and strain resolutions of 59 mK and 1.6 με, respectively. Given its dynamic capabilities and adjustable measurand resolution (e.g. temperature or strain resolution) through signal processing, this cost-effective approach offers significant potential for a variety of applications.
Publication Reference
IEEE Sensors Journal
Year
2025-03-15