Optical fiber temperature distribution measuring device

Patent metadata

Field	Value
Publication number	US-9835503-B2
Application number	US-201514751365-A
Country	US
Kind code	B2
Filing date	Jun 26, 2015
Priority date	Jul 16, 2014
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

An optical fiber temperature distribution measuring device includes: an optical fiber as a sensor; a calculation control unit for measuring a temperature distribution along the optical fiber by using backward Raman scattered light from the optical fiber; a far-end-position dispersion characteristic calculation unit for obtaining a dispersion characteristic of the optical fiber at a far-end position thereof; a per-unit-length dispersion characteristic calculation unit for obtaining a per-unit-length dispersion characteristic of the optical fiber based on the dispersion characteristic of the optical fiber at the far-end position thereof; and a correction parameter calculation unit for calculating a correction parameter for correcting a dispersion characteristic of the optical fiber based on a dispersion characteristic at each of different positions along the optical fiber.

First claim

What is claimed is:

1. An optical fiber temperature distribution measuring device comprising:
an optical fiber as a sensor; and
a calculation control unit configured to measure a temperature distribution along the optical fiber by using backward Raman scattered light from the optical fiber to calculate an intensity ratio between the intensity (Ias) of anti-Stokes light and the intensity (Ist) of Stokes light, the calculation control unit comprising:
a far-end-position dispersion characteristic calculation unit configured to obtain a dispersion characteristic (D end ) of the optical fiber at a far-end position thereof based on a response characteristic (A) of a body of the optical fiber temperature distribution measuring device and a response characteristic (H) of the optical fiber at the far-end position thereof, the dispersion characteristic being due to a variation of a distance over which the backward Raman scattered light travels through the optical fiber depending on the wavelength;
a per-unit-length dispersion characteristic calculation unit configured to obtain a per-unit-length dispersion characteristic (D 0 ) of the optical fiber based on the dispersion characteristic (D end ) of the optical fiber at the far-end position thereof; and
a correction parameter calculation unit configured to calculate a correction parameter for correcting a dispersion characteristic of the optical fiber based on the per-unit-length dispersion characteristic (D 0 ) of the optical fiber.

2. The optical fiber temperature distribution measuring device according to claim 1 , wherein
the far-end-position dispersion characteristic calculation unit is further configured to obtain the dispersion characteristic (D end ) of the optical fiber at the far-end position thereof by convoluting an inverse characteristic (F −1 ) of a characteristic (F) of a filter for removing a noise component on a high-frequency side and an inverse characteristic (A −1 ) of the response characteristic (A) of the body of the optical fiber temperature distribution measuring device with the response characteristic (H) of the optical fiber at the far-end position thereof.

3. The optical fiber temperature distribution measuring device according to claim 1 , wherein
the correction parameter calculation unit is further configured to obtain the correction parameter by performing a convolution calculation of an inverse characteristic (D X −1 ) of a dispersion characteristic (D X ) at each of different positions (X) along a distance direction of the optical fiber and an inverse characteristic (A −1 ) of the response characteristic (A) of the body of the optical fiber temperature distribution measuring device.

4. The optical fiber temperature distribution measuring device according to claim 3 , wherein
the correction parameter calculation unit is further configured to obtain the dispersion characteristic (D X ) at each of different positions along the optical fiber and the inverse characteristic (D X −1 ) thereof from the per-unit-length dispersion characteristic (D 0 ) of the optical fiber.

5. The optical fiber temperature distribution measuring device according to claim 1 , wherein the calculation control unit further comprising:
an averaging calculation unit configured to obtain a linear value of Stokes light and a linear value of anti-Stokes light by averaging the Stokes light and the anti-Stokes light, respectively, of the backward Raman scattered light; and
a spatial resolution calculation unit configured to perform a calculation of convoluting the correction parameter with the linear value of the Stokes light and the linear value of the anti-Stokes light.

6. The optical fiber temperature distribution measuring device according to claim 5 , wherein
the far-end-position dispersion characteristic calculation unit is further configured to obtain the dispersion characteristic (D end ) of the optical fiber at the far-end position thereof by performing a first calculation of convoluting a characteristic (F) of a filter for removing a noise component on a high-frequency side with the linear value of the Stokes light and the linear value of the anti-Stokes light, and a second calculation of convoluting an inverse characteristic (F −1 ) of the characteristic (F) of the filter and an inverse characteristic (A −1 ) of the response characteristic (A) of the body of the optical fiber temperature distribution measuring device with a result obtained by the first calculation.

7. The optical fiber temperature distribution measuring device according to claim 1 , wherein
the far-end-position dispersion characteristic calculation unit is further configured to obtain the dispersion characteristic (D end ) of the optical fiber at the far-end position thereof by convoluting the response characteristic (H) of the optical fiber at the far-end position thereof with an inverse characteristic (A −1 ) of the response characteristic (A) of the body of the optical fiber temperature distribution measuring device.

8. The optical fiber temperature distribution measuring device according to claim 7 , wherein
the calculation control unit is further configured to obtain the response characteristic (H) of the optical fiber at the far-end position thereof using a known parameter of the optical fiber.

9. The optical fiber temperature distribution measuring device according to claim 8 , wherein
the calculation control unit is further configured to obtain the response characteristic (A) of the body of the optical fiber temperature distribution measuring device based on a result of a level measurement of the backward Raman scattered light of the body of the optical fiber temperature distribution measuring device with the optical fiber, the optical fiber being unconnected to the body of the optical fiber temperature distribution measuring device.

Assignees

• Yokogawa Electric Corp

Inventors

• Shida Hideo

Classifications

• G01K11/32 Primary

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

• G01K2011/324

  Physics · mapped topic

• G01K11/324

  using Raman scattering · CPC title