Measurement apparatus and measurement method

Patent metadata

Field	Value
Publication number	US-10234337-B2
Application number	US-201715403433-A
Country	US
Kind code	B2
Filing date	Jan 11, 2017
Priority date	Mar 4, 2016
Publication date	Mar 19, 2019
Grant date	Mar 19, 2019

Abstract

The light source unit generates probe light. The splitting unit splits Brillouin backscattered light, which arise in the optical fiber under test owing to the probe light, into two branches of a first light path and a second light path. The delay unit gives a delay between light propagating through the first light path and the second light path. The multiplexer unit multiplexes light propagating through the first light path and the second light path to generate multiplexed light. The coherent detection unit performs heterodyne detection on the multiplexed light to output a difference frequency as a first electrical signal. The frequency shift amount obtaining unit performs homodyne detection on one of the two branches split from the first electrical signal and the second electrical signal having the same frequency as the frequency of the first electrical signal to obtain a frequency shift amount. The signal intensity obtaining unit generates intensity information of the first electrical signal as an intensity signal. The signal processing unit obtains strain δε and a temperature change δT separately from the frequency shift amount and the intensity.

First claim

What is claimed is:

1. A measurement apparatus comprising:
a light source unit configured to generate probe light;
a splitting unit configured to split Brillouin backscattered light into two branches of first light and second light, the Brillouin backscattered light arising owing to the probe light in a propagation medium which propagates light;
an optical frequency shifter unit provided in any one of a first light path configured to propagate the first light and a second light path configured to propagate the second light and configured to give a frequency shift of a beat frequency;
a delay unit provided in any one of the first light path and the second light path;
a multiplexer unit configured to multiplex light propagating through the first light path and the second light path to generate multiplexed light;
a coherent detection unit configured to perform heterodyne detection on the multiplexed light to output a difference frequency as a first electrical signal;
an electrical signal generating unit configured to generate a second electrical signal having the same frequency as a frequency of the first electrical signal;
a frequency shift amount obtaining unit configured to perform homodyne detection on the first electrical signal and the second electrical signal to obtain a frequency shift amount;
a signal intensity obtaining unit configured to generate intensity information of the first electrical signal as an intensity signal; and
a signal processing unit configured to calculate strain δε and a temperature change δT in the propagation medium, respectively, based on the frequency shift amount and the intensity, by using a predetermined equation.

2. A measurement apparatus comprising:
a light source unit configured to generate probe light;
a splitting unit configured to split Brillouin backscattered light into two branches of first light and second light, the Brillouin backscattered light arising owing to the probe light in a propagation medium which propagates light;
a first optical frequency shifter unit which is provided in the first light path configured to propagate the first light and configured to give a frequency shift of a first frequency;
a second optical frequency shifter unit which is provided in the second light path configured to propagate the second light and configured to give a frequency shift of a second frequency;
a delay unit provided in any one of the first light path and the second light path;
a multiplexer unit configured to multiplex light propagating through the first light path and the second light path to generate multiplexed light;
a coherent detection unit configured to perform heterodyne detection on the multiplexed light to output a difference frequency as a first electrical signal;
an electrical signal generating unit configured to generate a second electrical signal having the same frequency as a frequency of the first electrical signal;
a frequency shift amount obtaining unit configured to perform homodyne detection on the first electrical signal and the second electrical signal to obtain a frequency shift amount;
a signal intensity obtaining unit configured to generate intensity information of the first electrical signal as an intensity signal; and
a signal processing unit configured to calculate strain δε and a temperature change δT in the propagation medium, respectively, based on the frequency shift amount and the intensity, by using a predetermined equation.

3. The measurement apparatus according to claim 1 , wherein
to calculate strain δε and a temperature change δT in the propagation medium, the signal processing unit solves following simultaneous equations (1) with two unknowns with a frequency shift amount δν SDH and intensity δP B /P B , and a coefficient C νε of strain dependence and a coefficient C νT of temperature dependence of frequency shift of Brillouin backscatter, and a coefficient C Pε of strain dependence and a coefficient C PT of temperature dependence of a scattering coefficient of Brillouin backscatter in the propagation medium preliminarily obtained.

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Assignees

• Oki Electric Ind Co Ltd

Inventors

• Koizumi Kengo

Classifications

• G01D5/35364 Primary

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

• G01D5/28

  with deflection of beams of light, e.g. for direct optical indication (G01D5/40 takes precedence; {mechanical adjustment G01D5/264}) · CPC title

• G01K11/32

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

• G01K11/3206 Primary

  at discrete locations in the fibre, e.g. using Bragg scattering · CPC title

• G01K2011/322

  Physics · mapped topic