Distributed Dynamic Strain Sensing Based on Brillouin Scattering in Optical Fibers

Abstract

Over the past three decades, extensive research activity on Brillouin scattering-based distributed optical fiber sensors has led to the availability of commercial instruments capable of measuring the static temperature/strain distribution over kilometer distances and with high spatial resolution, with applications typically covering structural and environmental monitoring. At the same time, the interest in dynamic measurements has rapidly grown due to the relevant number of applications which could benefit from this technology, including structural analysis for defect identification, vibration detection, railway traffic monitoring, shock events detection, and so on. In this paper, we present an overview of the recent advances in Brillouin-based distributed optical fiber sensors for dynamic sensing. The aspects of the Brillouin scattering process relevant in distributed dynamic measurements are analyzed, and the different techniques are compared in terms of performance and hardware complexity.

Distributed cryogenic temperature sensing through Brillouin optical frequency-domain analysis

“…The choice of a PMF was done to avoid any Brillouin gain fluctuations by small movements of the fiber during the measurements. Indeed, in slope-assisted measurements any variation in the intensity of the collected signal can be misinterpreted as due to temperature or strain [9]. Although no attempt was made to align the pump and probe beams to the principal axes of the PMF, no polarization-induced spatial variation of the Brillouin gain was observed, because the beat length of our PMF (< 5 mm) was much smaller than the measuring spatial resolution of 16 mm.…”

“…In this work, we demonstrate the use of a Brillouin sensor operating in the frequency-domain for distributed temperature measurements at the liquid nitrogen temperature. Dynamic tests were also performed using a slope-assisted technique [9], combined with real-time signal processing techniques. The results are validated against temperature measurement based on conventional point-based sensors (thermocouples and fiber Bragg gratings (FBG)).…”

Overcoming the Lead Fiber-Induced Limitation on Pulse Repetition Rate in Distributed Fiber Sensors

“…where L, n g , and c are the length of the FUT, group refractive index of the fiber, and speed of light in a vacuum, respectively [18][19][20]. The MPRR is limited by RTT, which can be described by the equation for R mpp :…”

Long Range Raman-Amplified Distributed Acoustic Sensor Based on Spontaneous Brillouin Scattering for Large Strain Sensing

“…This limitation restricts the use of φ-DAS in applications that require measurement of high strain-rates over long distances such as analysis of large-magnitude earthquakes or evaluation of railway track behavior [3,17]. Although, a number of φ-DAS systems capable of measuring relatively large strain levels have recently been demonstrated, the sensing range in none of those studies were exceeding [18][19][20][21].…”