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Optical fiber strain measurement apparatus and optical fiber strain measurement method

A technology of optical fiber strain and measuring device, which is applied in the direction of measuring device, adopting optical device, converting sensor output, etc., can solve the problems that cannot be directly applied to directly modulated semiconductor laser, and achieve the effect of high receiving sensitivity

Active Publication Date: 2019-04-02
OKI ELECTRIC IND CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0024] Therefore, directly modulated semiconductor lasers cannot be directly applied to BOTDR

Method used

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  • Optical fiber strain measurement apparatus and optical fiber strain measurement method
  • Optical fiber strain measurement apparatus and optical fiber strain measurement method
  • Optical fiber strain measurement apparatus and optical fiber strain measurement method

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no. 1 Embodiment approach

[0039] refer to Figure 1~3 A first embodiment of the optical fiber strain measuring device of the present invention will be described. figure 1 It is a schematic block diagram of the first embodiment of the optical fiber strain measuring device. figure 2 is a graph showing spectral waveforms. exist figure 2 In (A) to (C), the horizontal axis represents the wavelength, and the vertical axis represents the signal intensity. figure 2 (A) represents a spectral waveform output from a direct modulation light source described later, figure 2 (B) shows the spectral waveform output from the optical band-pass filter (BPF) on the transmission side, figure 2 (C) shows the spectral waveform of backscattered light. image 3 It is a diagram showing an optical pulse waveform output from a transmission-side optical band-pass filter (BPF). exist image 3 In , the horizontal axis represents time, and the vertical axis represents signal strength.

[0040] The optical fiber strain m...

no. 2 Embodiment approach

[0067] In BOTDR, when the amount of data increases due to elongation or the like, the spatial resolution may be lowered to reduce the number of samples. In order to lower the spatial resolution, it is necessary to increase the optical pulse width.

[0068] Here, when the optical pulse width is changed, the duty ratio of the signal changes, and the wavelength corresponding to the ON level changes. Figure 4 It is a figure which shows the spectral waveform when the optical pulse width changes.

[0069] exist Figure 4 Among them, the case where the light pulse width is 31.25 ns is shown by curve I, and the case where the light pulse width is 50 ns is shown by curve II.

[0070] When the optical pulse width is increased, the peak of the ON level approaches the peak of the OFF level (noise). That is, since the wavelength of the probe light changes, the wavelength band of Brillouin scattering also changes.

[0071] Therefore, in the optical fiber strain measuring device accordi...

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Abstract

The invention relates to an optical fiber strain measurement apparatus and an optical fiber strain measurement method, aiming to enable a directly-modulated semiconductor laser to be applied as a light source of probe light. The optical fiber strain measurement apparatus includes a transmission unit configured to generate probe light, and a reception unit including a receiver-side optical bandpassfilter that extracts a Stokes component of Brillouin backscattered light from backscattered light which is caused by the probe light in a measurement target optical fiber, and a self-delayed heterodyne interferometer that detects a change in a frequency shift amount of the Stokes component as a phase difference are included. The transmission unit includes a directly-modulated light source configured to generate an optical pulse, and a transmitter-side optical bandpass filter provided in a stage following the directly-modulated light source, and configured to transmit wavelength of an ON levelof the optical pulse as the probe light, and block wavelength of an OFF level.

Description

technical field [0001] The invention relates to an optical fiber strain measuring device and an optical fiber strain measuring method using Brillouin scattered light. Background technique [0002] With the development of optical fiber communication, distributed optical fiber sensing using optical fiber itself as the sensing medium is being actively studied. In distributed optical fiber sensing, the representative one is time domain reflectometer (OTDR: Optical Time Domain Reflectometry: Optical Time Domain Reflectometry). Backscattered light was measured over time. Backscattering in optical fiber includes Rayleigh scattering, Brillouin scattering and Raman scattering. Among them, an instrument for measuring natural Brillouin scattering is called BOTDR (Brillouin OTDR: Brillouin Optical Time Domain Reflectometer) (see, for example, Non-Patent Document 1). [0003] Brillouin scattering is observed at a position shifted by about GHz to the Stokes side and anti-Stokes side re...

Claims

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Application Information

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IPC IPC(8): G01B11/16
CPCG01B11/16G01D5/35335G01D5/35364
Inventor 岩村英志
Owner OKI ELECTRIC IND CO LTD
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