In this paper we propose a novel kind of quasi-distributed polarimetric vibration sensor. Its functioning is based on the
use of mechanical transducers, which transform the mechanical vibration into a birefringence variation, and of fiber
Bragg gratings (FBGs), which reflect light from different positions. As it will be shown this sensor can provide the
vibration frequency in a quasi-distributed manner.
This paper presents the design of a mechanical transducer for an optical-fiber accelerometer based on polarization
variation. Several transducers can be imagined using either bending, twist, stretching or crushing of
the fiber. The transducers are modelled analytically and are compared through the curve representing the
sensitivity in function of the sensor resonant frequency. It turns out that the use of crushing shows a sensitivity
several orders of magnitude higher than the other deformations. In this latter case, experimental results
confirm the analytical computation of the sensitivity.
In this paper we propose a novel kind of quasi-distributed vibration sensor based on the measurement of the polarization
state of light. Its principle is based on the combination of mechanical transducers -which transform the mechanical
perturbation into a birefringence variation- with fiber Bragg gratings. We show that several vibrations can be detected
and localized at each transducer position with a frequency resolution of 1.25 Hz.
KEYWORDS: Signal to noise ratio, Spatial resolution, Receivers, Signal attenuation, Data acquisition, Fiber optics, Physics, Fiber optics sensors, Scattering, Temperature metrology
The signal-to-noise ratio (SNR) enhancement using a coded pulse in Brillouin Optical Time Domain Analysis (BOTDA)
is studied theoretically and experimentally and compared with the one pulse case. This new technique is based on
simplex coding and provides a theoretical SNR enhancement of 3.6 dB. We find that the experimental SNR
improvement is around 3.8 dB, which is in good accordance with the theory. We also observe that the Differential
Pulsewidth Pair - Brillouin Optical Time Domain Analysis (DPP-BOTDA) method can be applied. This allows to
combine high spatial and frequency resolutions1 and higher SNR.
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