Method and system for measuring an optical loss value of an optical fiber link

Patent metadata

Field	Value
Publication number	US-9709460-B2
Application number	US-201414575409-A
Country	US
Kind code	B2
Filing date	Dec 18, 2014
Priority date	Dec 20, 2013
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

The reflectometric method for measuring an optical loss value of an optical fiber link generally comprises: obtaining at least one bias value being indicative of a bias induced by differing backscattering characteristics of a first optical fiber length and a second optical fiber length; propagating at least one test signal serially into the first optical fiber length, the optical fiber link and the second optical fiber length; monitoring at least one return signal resulting respectively from the propagation of the at least one test signal; and determining the optical loss value based on the at least one return signal and the at least one bias value.

First claim

What is claimed is:

1. A reflectometric method for measuring an optical loss value of an optical fiber link, the method comprising:
obtaining at least one bias value being indicative of a bias induced by differing backscattering characteristics of a first optical fiber length and a second optical fiber length;
propagating at least one test signal serially into the first optical fiber length, the optical fiber link and the second optical fiber length;
monitoring at least one return signal resulting respectively from the propagation of the at least one test signal; and
determining the optical loss value based on the at least one return signal and the at least one bias value.

2. The reflectometric method of claim 1 , wherein said determining comprises:
determining a preliminary optical loss value based on the at least one return test signal; and
measuring the optical loss value by adjusting the preliminary optical loss value based on the at least one bias value.

3. The reflectometric method of claim 1 , wherein said determining comprises:
adjusting at least one portion of the at least one return signal with a corresponding one of the at least one bias value; and
measuring the optical loss value based on the adjusted at least one return signal.

4. The reflectometric method of claim 1 , wherein the reflectometric method is a single-ended Optical Time-Domain Reflectometric (OTDR) method, wherein the test signal comprises at least one test light pulse and wherein the return signal is obtained by propagating the at least one test light pulse into and along a complete optical fiber path made of the first optical fiber length having one end connected to an end of the optical fiber link and the other end of the optical fiber link connected to an end of the second fiber length; and detecting the corresponding return signal from the complete optical fiber path as a function of time so as to obtain a reflectometric trace representing backscattered and reflected light from the at least one test signal as a function of distance of the complete optical fiber path.

5. The reflectometric method of claim 2 , wherein said obtaining at least one bias value further comprises obtaining a bias value corresponding to a calibration optical fiber link having a connection between the first optical fiber length and the second optical fiber length.

6. The reflectometric method of claim 5 , wherein said obtaining a bias value corresponding to a calibration optical link further comprises obtaining a forward-measured connection loss value and a backward-measured connection loss value, each of the connection loss values representative of a difference in the backscattering level occurring in the calibration optical link at the connection between the first optical fiber length and the second optical fiber length, and wherein the bias value is based on the forward-measured connection loss value and the backward-measured connection loss value.

7. The reflectometric method of claim 6 , wherein the bias value is proportional to the difference between the forward-measured connection loss value and the backward-measured connection loss value.

8. The reflectometric method of claim 3 , wherein said obtaining at least one bias value further comprises obtaining a first relative bias value corresponding to a first calibration optical fiber link having a first connection between the first optical fiber length and a reference optical fiber; and obtaining a second relative bias value corresponding to a second calibration optical fiber link having a second connection between the reference optical fiber and the second optical fiber length.

9. The reflectometric method of claim 8 , wherein said obtaining a first relative bias value corresponding to a first calibration optical fiber link further comprises obtaining a first forward-measured connection loss value and a first backward-measured connection loss value; wherein said obtaining a second relative bias value corresponding to a second calibration optical fiber link further comprises obtaining a second forward-measured connection loss value and a second backward-measured connection loss value; wherein each of the connection loss values being representative of a difference in the backscattering level occurring along the corresponding calibration optical link at the position of the corresponding connection; and wherein the first and second relative bias value are based on the corresponding forward-measured connection loss values and the backward-measured connection loss values.

10. The reflectometric method of claim 8 , wherein said determining the optical loss value further comprises adjusting first and second portions of the at least one return signal with the corresponding first and second relative bias value; and measuring the optical loss value based on the adjusted at least one return signal.

11. The reflectometric method of claim 1 , wherein said obtaining at least one bias value further comprises obtaining an additional bias value being indicative of a bias induced by differing backscattering characteristics of the second optical fiber length and a third optical fiber length; wherein said propagating further comprises propagating the at least one test signal from the second optical fiber length directly into an additional optical fiber link, from the additional optical fiber link directly into a third optical fiber length for propagation therealong; and wherein said determining further comprises determining an additional optical loss corresponding to said additional optical fiber link based on the at least one return signal and the additional bias value.

12. The reflectometric method of claim 1 , wherein the first optical fiber length is included in a multiplicity of first optical fiber lengths and the second optical fiber length is included in a multiplicity of second optical fiber lengths; wherein each of a plurality of optical fiber links is connectable in-between corresponding first and second optical fiber lengths of the multiplicities.

13. The reflectometric method of claim 1 , wherein the second optical fiber length is connected to a signature device having a reflectance signature to form an encoded receive device, and wherein the method further comprises recognizing said signature using the monitored at least one return signal to confirm a continuity of the optical fiber link.

14. The reflectometric method of claim 13 , wherein the reflectance signature is provided by a reflective member located at a specific distance from the optical fiber link.

15. The reflectometric method of claim 13 , wherein the encoded device is split into a first arm and a second arm, the first arm having a first reflective member located at a first distance from the optical fiber link, the second arm having a second reflective member located at a second distance from the optical fiber link.

16. A system for measuring an optical loss value occurring along an optical fiber link, the system comprising:
an optical test signal generator for generating a test signal to be propagated serially along a first optical fiber length, the optical fiber link and a second optical fiber length, the first optical fiber length and the second optical fiber length being characterized by a bias value indicative of a bias induced by differing backscattering characteristics of the first optical fiber length and the second optical fiber length;
an optical detector for monitoring a return signal resulting from the propagation of the test signal; and
a processor configured for determining an optical loss value based on the return signal and

Assignees

• Exfo Inc

Inventors

• Leblanc Michel
• Perron Stéphane

Classifications

• G01M11/3172

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

• G01M11/3145 Primary

  Details of the optoelectronics or data analysis · CPC title

• G01M11/31 Primary

  with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers · CPC title