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

Abstract

A Brillouin distributed acoustic sensor (DAS) based on optical time-domain refractometry exhibiting a maximum detectible strain of 8.7 mε and a low signal fading is developed. Strain waves with frequencies of up to 120 Hz are measured with an accuracy of 12 με at a sampling rate of 1.2 kHz and a spatial resolution of 4 m over a sensing range of 8.5 km. The sensing range is further extended by using a modified inline Raman amplifier configuration. Using 80 ns Raman pump pulses, the signal-to-noise ratio is improved by 3.5 dB, while the accuracy of the measurement is enhanced by a factor of 2.5 to 62 με at the far-end of a 20 km fiber.

Trackbed behavior analysis based on distributed acoustic sensor

“…For distributed sensing, spatial and temporal resolution as well as the sampling rate of the DAS system need to be adjusted relative to the physical characteristics of the phenomena of interest. For instance, the spatial resolution of the DAS interrogator should be shorter than the length of the train wheel while the sampling rate of the interrogator should be high enough to allow measurement of a high strain rate through fringe counting [7].…”