Test method for characterizing an optical fiber link

Patent metadata

Field	Value
Publication number	US-11480496-B2
Application number	US-202117198686-A
Country	US
Kind code	B2
Filing date	Mar 11, 2021
Priority date	Dec 19, 2018
Publication date	Oct 25, 2022
Grant date	Oct 25, 2022

Abstract

There is provided a test method and system for characterizing an optical fiber link. At least one OTDR acquisition or at least one OLTS acquisition is performed on the optical fiber link. From the acquisition, a value of an excess insertion loss and/or an excess optical return loss associated with the optical fiber link under test is derived, i.e. in excess of a nominal value associated with a hypothetical optical fiber link having a length corresponding to the total length of the optical fiber link under test. A rating value (e.g., as a five-star rating) or a binary pass/fail value associated with the optical fiber link under test can then be derived and displayed.

First claim

The invention claimed is:

1. A method for characterizing an optical fiber link under test, the method comprising:
performing at least one OTDR acquisition toward the optical fiber link, wherein the OTDR acquisition comprises propagating in the optical fiber link under test, a pulsed test signal and detecting corresponding return light from the optical fiber link representing backscattered and reflected light as a function of distance in the optical fiber link; and
from the OTDR acquisition, deriving a value of an excess insertion loss associated with the optical fiber link under test, in excess of a nominal value of insertion loss associated with a hypothetical optical fiber link having a length corresponding to the total length of the optical fiber link under test.

2. The method as claimed in claim 1 , further comprising:
from the OTDR acquisition, deriving a measured value of total length of said optical fiber link and a measured value of insertion loss associated with the optical fiber link under test.
calculating a nominal value of insertion loss associated with said hypothetical optical fiber link having a length corresponding to the measured value of total length; and
deriving said value of said excess insertion loss associated with the optical fiber link under test by deducting the nominal value of insertion loss from the measured value of insertion loss.

3. The method as claimed in claim 2 , wherein the nominal value is calculated at least from the measured value of total length and a value of at least one constant of proportionality.

4. The method as claimed in claim 3 , further comprising:
deriving a rating value associated with the optical fiber link, at least from the derived value of excess insertion loss; and
outputting said rating value.

5. The method as claimed in claim 3 , further comprising:
deriving a binary pass/fail value associated with the optical fiber link, at least from the derived value of excess insertion loss; and
outputting said binary pass/fail value.

6. The method as claimed in claim 1 , further comprising deriving a value of excess back reflections associated with the optical fiber link under test, in excess of a nominal value of back reflections associated with a hypothetical optical fiber link having a length corresponding to the total length of the optical fiber link under test.

7. The method as claimed in claim 6 , wherein deriving a value of excess back reflections comprises:
from the OTDR acquisition, calculating the excess back reflections by integrating portions of the OTDR acquisition corresponding to reflectance peaks.

8. The method as claimed in claim 7 , further comprising:
deriving a value of backward-direction excess back reflections;
deriving a rating value associated with the optical fiber link, at least from a maximum of the derived value of excess back reflections and the derived value of backward-direction excess back reflections; and
outputting said rating value.

9. The method as claimed in claim 6 , further comprising deriving a first rating value associated with the optical fiber link from the derived value of excess insertion loss and deriving a second rating value associated with the optical fiber link from the derived value of excess back reflections.

10. The method as claimed in claim 9 , further comprising deriving a global rating value associated with the optical fiber link as the weakest of the first rating value and the second rating value.

11. The method as claimed in claim 1 , further comprising:
deriving a first binary pass/fail value associated with the optical fiber link from the derived value of excess insertion loss;
identifying at least one event along the optical fiber link from the at least one OTDR acquisition and deriving a measured value of insertion loss associated with the identified event;
deriving a second binary pass/fail value associated with the identified event, at least from the measured value of insertion loss associated with the identified event; and
deriving a global binary pass/fail value associated with the optical fiber link at least from a combination of the first binary pass/fail value and the second binary pass/fail value.

12. The method as claimed in claim 1 , further comprising:
deriving a first rating value associated with the optical fiber link from the derived value of excess insertion loss;
identifying at least one event along the optical fiber link from the at least one OTDR acquisition and deriving a measured value of insertion loss associated with the identified event;
deriving a second rating value associated with the identified event, at least from the measured value of insertion loss associated with the identified event; and
deriving a global rating value associated with the optical fiber link at least from a combination of the first rating value and the second rating value.

13. A method for characterizing an optical fiber link, the method comprising:
performing at least one OTDR acquisition toward the optical fiber link, wherein the OTDR acquisition comprises propagating in the optical fiber link under test, a pulsed test signal and detecting corresponding return light from the optical fiber link representing backscattered and reflected light as a function of distance in the optical fiber link; and
from the OTDR acquisition, deriving a rating value associated with the optical fiber link, related to a value of an excess insertion loss associated with the optical fiber link under test, in excess of a nominal value of insertion loss associated with a hypothetical optical fiber link having a length corresponding to the total length of the optical fiber link under test.

14. The method as claimed in claim 13 , further comprising:
from the OTDR acquisition, deriving a measured value of total length of said optical fiber link and a measured value of an insertion loss associated with the optical fiber link;
calculating a nominal value of insertion loss associated with a hypothetical optical fiber link having a length corresponding to the measured value of total length; and
deriving a value of an excess insertion loss by deducting the nominal value of said first parameter from the measured value of the first parameter.

15. An OTDR system for characterizing an optical fiber link, the OTDR system comprising:
an OTDR acquisition device connectable toward an end of the optical fiber link for performing at least one OTDR acquisition toward the optical fiber link, wherein each OTDR acquisition is performed by propagating in the optical fiber link under test, a pulsed test signal and detecting corresponding return light from the optical fiber link representing backscattered and reflected light as a function of distance in the optical fiber link; and
a processing unit receiving the OTDR trace and configured to:
from the OTDR acquisition, derive a measured value of total length of said optical fiber link and a measured value of the insertion loss associated with the optical fiber link;
calculate a nominal value of insertion loss associated with said hypothetical optical fiber link having a length corresponding to the measured value of total length; and
derive a value of an excess insertion loss associated with the optical fiber link under test, in excess of the nominal value.

16. The OTDR system as claimed in claim 15 , wherein:
the processing unit is further configured to derive a rating value associated with the optical fiber link, at least from the derived value of excess insertion loss; and
the OTDR system further comprises a display to display said rating value

Assignees

• Exfo Inc

Inventors

• Perron Stephane
• Thomassin Eric

Classifications

• G01M11/3145 Primary

  Details of the optoelectronics or data analysis · CPC title

• G01D5/268

  using optical fibres (G01D5/28 - G01D5/38 take precedence) · CPC title

• G01B11/02

  for measuring length, width or thickness (G01B11/08 takes precedence) · CPC title

• G01M11/3127 Primary

  using multiple or wavelength variable input source · CPC title