Optical fiber characteristic measuring device

Patent metadata

Field	Value
Publication number	US-9983095-B2
Application number	US-201615255545-A
Country	US
Kind code	B2
Filing date	Sep 2, 2016
Priority date	Sep 7, 2015
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

An optical fiber characteristic measuring device of the present invention includes a light source, an optical divider, an optical waveguide, a first separator, a second separator, a first interferer, a second interferer, and a calculator. The light source is configured to generate a frequency modulated continuous wave of light. The optical divider is configured to divide the frequency modulated continuous wave of light into first and second divided-waves of light. The optical waveguide is configured to guide the first divided-wave of light to one end of an optical fiber to be measured. The first separator is configured to separate a backscattered light generated by Brillouin scattering of the first divided-wave of light in the optical fiber to be measured into a first scattered light, which is a linearly polarized light, and a second scattered light, which is a linearly polarized light perpendicular to the first scattered light.

First claim

What is claimed is:

1. An optical fiber characteristic measuring device comprising:
a light source configured to generate a frequency modulated continuous wave of light;
an optical divider configured to divide the frequency modulated continuous wave of light into first and second divided-waves of light;
an optical waveguide configured to guide the first divided-wave of light to one end of an optical fiber to be measured;
a first separator configured to separate a backscattered light generated by Brillouin scattering of the first divided-wave of light in the optical fiber to be measured into a first scattered light, which is a linearly polarized light, and a second scattered light, which is a linearly polarized light perpendicular to the first scattered light;
a second separator configured to separate the second divided-wave of light into a first divided-sub-wave of light having an identical polarization state with the first scattered light and a second divided-sub-wave of light having an identical polarization state with the second scattered light;
a first interferer configured to allow the first scattered light and the first divided-sub-wave of light to interfere with each other to generate a first beat component;
a second interferer configured to allow the second scattered light and the second divided-sub-wave of light to interfere with each other to generate a second beat component; and
a calculator configured to calculate characteristics of the optical fiber to be measured on the basis of the first beat component and the second beat component,
wherein the calculator comprises:
a first analyzer configured to analyze the first beat component based on Brillouin scattered light generated at a first position in the optical fiber to be measured to generate a first spectrum;
a second analyzer configured to analyze the second beat component based on the Brillouin scattered light generated at the first position to generate a second spectrum; and
a controller configured to control starting and stopping of the first analyzer and the second analyzer,
wherein when there are a plurality of correlation peaks, in which a frequency difference between the backscattered light and the second divided-wave of light is not temporally changed, in the optical fiber to be measured, the controller controls the starting and stopping of the first analyzer to measure a first spectrum of the first beat component associated with one correlation peak, which is needed and based on the Brillouin scattered light generated at the first position, among the plurality of correlation peaks, and controls the starting and stopping of the second analyzer to measure a second spectrum of the second beat component associated with the correlation peak based on the Brillouin scattered light generated at the first position.

2. The optical fiber characteristic measuring device according to claim 1 , wherein the calculator comprises:
a synthesizer configured to synthesize the first spectrum and the second spectrum to generate a synthetic spectrum; and
a measurer configured to measure characteristics of the optical fiber to be measured at the first position on the basis of the synthetic spectrum.

3. The optical fiber characteristic measuring device according to claim 2 , wherein the synthesizer is configured to perform a process of adding a first component intensity obtained by squaring a component of the first spectrum at a frequency and a second component intensity obtained by squaring a component of the second spectrum at the frequency while changing the frequency to generate the synthetic spectrum.

4. The optical fiber characteristic measuring device according to claim 1 , wherein the first separator is a polarizing beam splitter.

5. The optical fiber characteristic measuring device according to claim 1 , wherein the second separator is a polarizing beam splitter.

6. The optical fiber characteristic measuring device according to claim 1 , wherein the first interferer is configured to separate the first beat component into two beat components at a first ratio.

7. The optical fiber characteristic measuring device according to claim 6 , wherein the second interferer is configured to separate the second beat component into two beat components at a second ratio.

8. The optical fiber characteristic measuring device according to claim 7 , further comprising:
a first photoelectric converter configured to convert one of two beat components separated by the first interferer into electric signals; and
a second photoelectric converter configured to convert the other of the two beat components separated by the first interferer into electric signals.

9. The optical fiber characteristic measuring device according to claim 8 , further comprising:
a third photoelectric converter configured to convert one of the two beat components separated by the second interferer into electric signals; and
a fourth photoelectric converter configured to convert the other of the two beat components separated by the second interferer into electric signals.

10. The optical fiber characteristic measuring device according to claim 9 , further comprising:
a first amplifier configured to amplify the electric signals output from the first photoelectric converter and the second photoelectric converter and input the amplified electric signals into the calculator.

11. The optical fiber characteristic measuring device according to claim 10 , further comprising:
a second amplifier configured to amplify the electric signals output from the third photoelectric converter and the fourth photoelectric converter and input the amplified electric signals into the calculator.

12. The optical fiber characteristic measuring device according to claim 1 , wherein the calculator is configured to calculate a strain distribution in a longitudinal direction of the optical fiber to be measured.

13. The optical fiber characteristic measuring device according to claim 1 , wherein the calculator is configured to calculate a temperature distribution in a longitudinal direction of the optical fiber to be measured.

14. The optical fiber characteristic measuring device according to claim 1 , wherein the calculator further comprises:
a local oscillator configured to supply a signal having a frequency to the first analyzer and the second analyzer.

Assignees

• Yokogawa Electric Corp

Inventors

• Matsuura Satoshi
• Furukawa Osamu

Classifications

• G01M11/3172 Primary

  Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection · CPC title

• G01D5/35364 Primary

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

• G01M11/3181

  Reflectometers dealing with polarisation · CPC title