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

Patent metadata

Field	Value
Publication number	US-10871406-B2
Application number	US-201816031604-A
Country	US
Kind code	B2
Filing date	Jul 10, 2018
Priority date	Sep 27, 2017
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

A self-delayed homodyne interferometer includes light source unit, a splitting unit, an interference signal acquisition unit, a scattered light intensity acquisition unit, and a signal processing unit. The light source unit generates probe light. The splitting unit splits into two branches, Brillouin backscattered light occurring in an optical fiber to be measured with the probe light. The acquisition unit receives scattered light of one branch, and uses a self-delayed homodyne interferometer to generate an interference signal. The acquisition unit receives scattered light of the other branch, and acquires intensity of the scattered light. The signal processing unit separates and acquires a frequency shift amount from the intensity of the interference signal, and strain and temperature change from the intensity of the scattered light. The acquisition unit can change a phase of the scattered light of the one of the two branches.

First claim

What is claimed is:

1. An optical fiber strain and temperature measurement apparatus comprising:
a light source unit configured to generate probe light;
a splitting unit configured to split Brillouin backscattered light into two branches, the Brillouin backscattered light occurring in an optical fiber to be measured with the probe light;
an interference signal acquisition unit configured to receive scattered light of one of the two branches split by the splitting unit, and use self-delayed homodyne interferometer to generate an interference signal;
a scattered light intensity acquisition unit configured to receive scattered light of another of the two branches split by the splitting unit, and acquire intensity of the scattered light; and
a signal processing unit configured to separate and acquire a frequency shift amount acquired from intensity of the interference signal, and strain δε and a temperature change δT from the intensity of the scattered light, wherein
the interference signal acquisition unit is capable of changing a phase of the scattered light of the one of the two branches.

2. The optical fiber strain and temperature measurement apparatus according to claim 1 , wherein
the signal processing unit acquires the strain δε and the temperature change δT in an optical fiber by solving following simultaneous equations (1) with two unknowns from the frequency shift amount δv and the intensity δP B /P B , a strain dependence coefficient C vε and a temperature dependence coefficient C vT of a frequency shift of Brillouin backscattering, and a strain dependence coefficient C Pε and a temperature dependence coefficient C PT of a scattering coefficient of the Brillouin backscattering in the optical fiber, the strain dependence coefficient C vε , the temperature dependence coefficient C vT , the strain dependence coefficient C Pε , and the temperature dependence coefficient C PT being obtained in advance

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3. The optical fiber strain and temperature measurement apparatus according to claim 1 , wherein
the interference signal acquisition unit includes
a self-delayed homodyne interferometer including
an interferometer splitting unit configured to split the received scattered light into two branches of a first light path and a second light path,
a delay adjustment unit provided in the first light path, and capable of changing the phase of the scattered light in accordance with an instruction from the signal processing unit

Assignees

• Oki Electric Ind Co Ltd

Inventors

• Koizumi Kengo
• Yamaguchi Tokuo
• Murai Hitoshi

Classifications

• G01D5/35364 Primary

  using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering · CPC title

• G01D5/35332

  using other interferometers · CPC title

• G01K11/322

  using Brillouin scattering · CPC title

• G01K11/32 Primary

  using changes in transmittance, scattering or luminescence in optical fibres · CPC title

• G01J3/4412

  Scattering spectrometry (particle sizing by light scattering G01N15/0205; optical velocimetry of particles G01P5/20, G01P5/26) · CPC title