Fiber sensing system based on a bragg grating and optical time domain reflectometry

By using continuously distributed weak fiber Bragg gratings and shaped signal pulse technology in the optical fiber, the balance problem between the sensor's measurement accuracy and spatial resolution is solved, and efficient distributed fiber sensing is achieved, eliminating blind spots and improving efficiency. Real-time monitoring capabilities for temperature and stress changes.

Inactive Publication Date: 2014-08-27
ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (EPFL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In systems of this type, however, two practical limitations clearly arise
First, the state of polarization (SOP) of the light wave can be preserved during longitudinal propagation of less than 1 km, severely limiting the maximum obtainable measurement range
Second, from a practical point of view, the complexity of the sensing system may become a practical limitation for its implementation in practical applications
Furthermore, the temperature and stress variations along the fiber are not uniform, distorting the original FBG spectrum (measured as a reference)
This means that the pre-calibration will become blurred, which will definitely reduce the measurement accuracy

Method used

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Embodiment Construction

[0030] Now, referring to the accompanying drawings, figure 1 A preferred schematic of the proposed distributed sensing system using long and weak fiber Bragg gratings to interrogate distributed temperature and / or stress along optical fibers is shown.

[0031] A weak and long fiber Bragg grating was used as the sensing fiber, and the temperature dependence of the peak frequency of the FBG was measured to be -1.23 GHz / K. After passing through a pulse shaping device, which may be an electro-optical modulator (EOM), a FWHM 50 ps signal pulse is generated and then sent into the FBG. Next, the center frequency of the pulses was increased in steps of a few MHz near the FBG reflection spectral window by simply changing the frequency of the tunable laser source (TLS).

[0032] In Fig. 2(a), the FBG used as a distributed sensor is shown. According to the present invention, a hot spot can be generated and precisely located using distributed FBG.

[0033] Figure 2(b) shows the measured...

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Abstract

Optic fiber sensor characterized in that the sensing fiber is provided with a continuous Bragg grating covering the entire fiber length which is dedicated to sensing and along which spatially resolved measurements are performed.

Description

technical field [0001] The invention relates to an optical fiber sensor and a sensing method including using the optical fiber sensor. Background technique [0002] Sensing fibers can be used in different applications, for example to control the functionality of fiber optic networks or to be installed on structures like sensory nervous systems. These sensing fibers are primarily used for detection and can perform a similar function to "strain gauges". [0003] The sensing fiber represents the physical condition of the main fiber optic line, and by detecting the operation of the sensing fiber, the environment of the main line can be determined. [0004] The glass optical fiber senses temperature or pressure and tension, which locally alters the optical transmission and reflection properties in the fiber. This sensing capability of glass fibers makes it possible to also include sensing fibers in long-distance pipelines (eg, delivery pipes) in order to detect and locate defor...

Claims

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Application Information

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Patent Type & AuthorityApplications(China)
IPC IPC(8): G01D5/353
CPCG01M11/3109G01J1/0425G01L1/246G02B6/34G01D5/35316G01K11/32
OwnerECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (EPFL)