Probe pulse design in Brillouin optical time‐domain reflectometry

Abstract

Brillouin optical time‐domain reflectometry (BOTDR) is a branch of distributed fibre‐optic sensors, and it can measure the strain and the temperature information, localised by the return time of the probe pulse, along the fibre based on the spontaneous Brillouin scattering process. Parameters of the BOTDR system, including the spatial resolution, the signal‐to‐noise ratio, the measurement speed, and the sensing range, have a mutually restrictive relationship. In order to improve the performance of the BOTDR system, researchers have focussed on improving the design of the probe pulse, for example, transforming the shape, the sequence, and the spectral properties of the pulse. This study summarises the recent progress in the design of detection pulses in BOTDR systems, and comprehensively demonstrates the improvement effects of various pulse modulation formats on the system performance.

Composite Bridge Girders Structure Health Monitoring Based on the Distributed Fiber Sensing Textile

“…The detected frequency shift can be used to determine the temperature or strain at that location. Since the scattered light experiences a Doppler frequency shift, the Brillouin shift V B can be expressed as [33]:…”

“…The detected frequency shift can be used to determine the temperature or strain at that location. Since the scattered light experiences a Doppler frequency shift, the Brillouin shift can be expressed as [ 33 ]: where is the effective refractive index of the sensing fiber, is the optical wavelength and the is the acoustic velocity. The strain applies in the fiber and has an effect on the speed of sound, resulting in a change in Brillouin frequency.…”

A Refinement of Backward Correlation Technique for Precise Brillouin Frequency Shift Extraction

“…If it is necessary to obtain information about each point of the sensor, it is advisable to use distributed fiberoptic sensors [7][8][9][10]. They can be based on Rayleigh [11], Raman [12], or Brillouin [13][14][15] scattering. The intensity of Rayleigh scattering in an optical fiber weakly depends on the impact applied; therefore, special methods of radiation phase extraction are used to obtain information about temperatures and strains [16].…”