Optical fiber temperature distribution measuring device

Patent metadata

Field	Value
Publication number	US-9631983-B2
Application number	US-201514708744-A
Country	US
Kind code	B2
Filing date	May 11, 2015
Priority date	May 13, 2014
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

An optical fiber temperature distribution measuring device measures a temperature distribution along an optical fiber by using backward Raman scattering light generated in the optical fiber. The device includes an arithmetic controller that changes a plurality of calibration parameters in conjunction with each other on the basis of a measured temperature value and a reference temperature value at a to-be-measured point, thereby converging a calibrated value of the measured temperature to a true value.

First claim

What is claimed is:

1. An optical fiber temperature distribution measuring device which measures a temperature distribution along an optical fiber by using backward Raman scattering light generated in the optical fiber, the device comprising:
an arithmetic controller that changes a plurality of calibration parameters in conjunction with each other on the basis of a measured temperature value and a reference temperature value at a to-be-measured point, thereby converging a calibrated value of the measured temperature to the reference temperature value based on a loss difference of Stokes light and anti-Stokes light in a longitudinal direction of the optical fiber.

2. The optical fiber temperature distribution measuring device according to claim 1 , wherein the calibration parameters are three parameters of a temperature offset, a shift wave number and the loss difference in the longitudinal direction of the optical fiber due to a wavelength difference between Stokes light and anti-Stokes light,
wherein the calibrated value is obtained by changing the loss difference and changing the shift wave number and the temperature offset in conjunction with the same.

3. An optical fiber temperature distribution measuring device which measures a temperature distribution along an optical fiber by using backward Raman scattering light generated in the optical fiber, the device comprising:
an arithmetic controller that solves a simultaneous equation on the basis of a measured temperature value and a reference temperature value at a to-be-measured point, thereby obtaining exact solutions of all calibration parameters,
wherein the optical fiber temperature distribution measuring device obtains optimal values of a shift wave number, a loss difference between Stokes light and anti-Stokes light, and a temperature offset, based on the measured temperature value and the reference temperature value at three to-be-measured points and a true loss difference.

4. The optical fiber temperature distribution measuring device according to claim 1 , wherein the calibrated value of the measured temperature is re-calculated and converged to the true value until a difference between the measured temperature and the reference temperature value is equal to or smaller than a desired value.

5. An optical fiber temperature distribution measuring device which measures a temperature distribution along an optical fiber by using backward Raman scattering light generated in the optical fiber, the device comprising:
an arithmetic controller that changes a plurality of calibration parameters in conjunction with each other on the basis of a measured temperature value and a reference temperature value at a to-be-measured point, thereby converging a calibrated value of the measured temperature to a true value based on a loss difference in a longitudinal direction of the optical fiber, wherein the measured temperature is re-calculated in view of the loss difference based on:

hc
⁢

⁢
Δ
⁢

⁢

v
0

kT
′

⁢
n

=

-
ln

⁢

⁢

R
⁡

(

Tn
,
Ln

)

-

ln
⁡

(

10

α
new

⁢

L
n

5

)

+

ln
⁢

⁢

R
⁡

(

T
0

)

+

hc
⁢

⁢
Δ
⁢

⁢

v
0

kT
0

,

wherein:
h: Planck constant (6.626×10 −34 Js),
c: light speed [m/s],
Δv 0 : Raman shift wave number [/m] of temperature reference unit,
k: Boltzmann constant (1.38×10 −23 JK −1 ),
α new : re-setting value [dB/km] of difference between losses of Stokes light ST and anti-Stokes light AS,
T′n: temperature distribution measured value [K] of to-be-measured point Ln at loss difference a new ,
T 0 : temperature [K] of temperature reference unit,
R(T, L): ratio (Ias/Ist) of anti-Stokes light Ias and Stokes light Ist at a to-be-measured point of any distance L,
R(T 0 ): ratio (Ias/Ist) of anti-Stokes light Ias and Stokes light Ist at temperature reference unit,
L: distance [m] from an emission end of the apparatus to a to-be-measured point.

6. The optical fiber temperature distribution measuring device according to claim 3 , wherein the simultaneous equation comprises:

Δ
⁢

⁢
v

=

Δ
⁢

⁢

v
0

×

(

Assignees

• Yokogawa Electric Corp

Inventors

• Oishi Kazushi
• Umeno Teruaki

Classifications

• G01K11/32 Primary

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

• G01K15/005

  Calibration · CPC title

• G01M11/3109

  Reflectometers detecting the back-scattered light in the time-domain, e.g. OTDR · CPC title

• G01K2011/324

  Physics · mapped topic

• G01K11/324

  using Raman scattering · CPC title