Bi-directional multi-pulsewidth optical time-domain reflectometer

Patent metadata

Field	Value
Publication number	US-9134197-B2
Application number	US-201314014606-A
Country	US
Kind code	B2
Filing date	Aug 30, 2013
Priority date	Jan 15, 2013
Publication date	Sep 15, 2015
Grant date	Sep 15, 2015

Abstract

There is provided a bi-directional optical reflectometric method for characterizing an optical fiber link. The method comprises: performing a plurality of forward-direction light acquisitions from one end of the optical fiber link and performing a plurality of backward-direction light acquisitions from the opposite end, wherein each light acquisition is performed by propagating at least one test light signal corresponding to given spatial resolution and detecting corresponding return light so as to obtain a reflectometric trace representing backscattered and reflected light as a function of a distance on the optical fiber link, and wherein said plurality of forward-direction light acquisitions and said plurality of backward-direction light acquisitions are each performed with mutually different spatial resolutions; and deriving a value of at least one parameter characterizing an event along said optical fiber link at least using a forward-direction light acquisition and a backward-direction light acquisition performed with mutually different spatial resolutions.

First claim

What is claimed is:

1. A bi-directional optical reflectometric method for characterizing an optical fiber link, the method comprising:
performing a plurality of forward-direction light acquisitions from one end of the optical fiber link and performing a plurality of backward-direction light acquisitions from the opposite end of the optical fiber link,
wherein each light acquisition is performed by propagating in the optical fiber link from the corresponding end, a test light signal corresponding to a given spatial resolution in the optical fiber link and detecting corresponding return light from the optical fiber link so as to obtain a reflectometric trace representing backscattered and reflected light as a function of distance on the optical fiber link, and
wherein said plurality of forward-direction light acquisitions and said plurality of backward-direction light acquisitions are each performed with mutually different spatial resolutions; and

deriving a value of at least one parameter characterizing an event along said optical fiber link at least using a forward-direction light acquisition and a backward-direction light acquisition performed with mutually different spatial resolutions.

2. The bi-directional reflectometric method as claimed in claim 1 ,
wherein each said light acquisition is an Optical Time-Domain Reflectometric (OTDR) light acquisition for which said test light signal comprises at least one test light pulse of a given pulsewidth;
wherein the pulsewidths corresponding to said plurality of forward-direction light acquisitions and to said plurality of backward-direction light acquisitions are mutually different; and
wherein said forward-direction light acquisition and said backward-direction light acquisition used for said deriving a value of at least one parameter are thereby performed with mutually different pulsewidths.

3. The bi-directional OTDR method as claimed in claim 2 , further comprising:
identifying events in said optical fiber link from return light of forward-direction light acquisitions to create a list of events wherein each event of said list is characterized at least by a location along said optical fiber link;
identifying events in said optical fiber link from return light of backward-direction light acquisitions to create a list of events wherein each event of said list is characterized at least by a location along said optical fiber link;
matching location of events in the forward-direction list with location of events in the backward-direction list to create a consolidated list of events comprising events of said forward-direction and said backward-direction list.

4. The bi-directional OTDR method as claimed in claim 2 , wherein said at least one parameter characterizing said event comprises a bi-directional loss parameter and wherein a value of said bi-directional loss parameter is derived from a selected one of forward-direction acquisitions obtained with a first pulsewidth and a selected one of backward-direction acquisitions obtained with a second pulsewidth different from said first pulsewidth.

5. The bi-directional OTDR method as claimed in claim 2 , wherein said at least one parameter characterizing said event comprises a bi-directional loss parameter and wherein deriving a value of the bi-directional loss parameter characterizing an event comprises:
associating a quality factor to said loss parameter for each of the forward-direction light acquisitions and for each of the backward-direction light acquisitions;
comparing the quality factors associated with each of the forward-direction light acquisitions to select one of the forward-direction light acquisitions to use for computing a value of a forward-direction loss parameter;
comparing the quality factors associated with each of the backward-direction light acquisitions to select one of the backward-direction light acquisitions to use for computing a value of a backward-direction loss parameter;
computing the bi-directional loss parameter characterizing the one event based on the forward- and backward-direction loss parameters.

6. The bi-directional OTDR method as claimed in claim 2 , further comprising:
deriving a value of at least another parameter characterizing said event using return light from a selected one of forward-direction light acquisitions and backward-direction light acquisitions.

7. The bi-directional OTDR method as claimed in claim 6 , wherein deriving a value of a parameter characterizing an event comprises:
associating a quality factor to said parameter for each of the forward-direction light acquisitions and for each of the backward-direction light acquisitions;
comparing the quality factors associated with each of the forward-direction and backward-direction light acquisitions to select one of the forward-direction or backward-direction light acquisitions to use for computing the value of the parameter.

8. The bi-directional OTDR method as claimed in claim 3 , wherein some events are merged together in one list of events but distinct in the other list of events and wherein said matching location of events matches said events as merged together in said one list with events as distinct in the other list to create the consolidated list.

9. The bi-directional OTDR method as claimed in claim 3 , wherein:
at least one event present in one of said forward-direction and said backward-direction lists is missing from the other one, said at least one event then being part of said consolidated list of events; and
the method further comprises deriving a value of an insertion loss parameter characterizing said at least one event based on return light from both a selected one of forward-direction acquisitions and a selected one of backward-direction acquisitions.

10. The bi-directional OTDR method as claimed in claim 2 , wherein a plurality of light acquisitions is performed with respective test light pulses having mutually different wavelengths.

11. The bi-directional OTDR method as claimed in claim 10 , further comprising:
identifying events in said optical fiber link from return light of acquisitions performed at a first wavelength to create a first list of events wherein each event of said list is characterized at least by a location along said optical fiber link;
identifying events in said optical fiber link from return light of acquisitions performed at a second wavelength to create a second list of events wherein each event of said second list is characterized at least by a location along said optical fiber link; and
matching location of events in the first list with location of events in the second list to create a consolidated list of events comprising events of said first and said second list, wherein said matching location of events matches some events that are merged together in one list of events with events as distinct in the other list of events to create the consolidated list.

12. The bi-directional OTDR method as claimed in claim 10 , further comprising:
identifying events in said optical fiber link from return light of acquisitions performed at a first wavelength to create a first list of events wherein each event of said first list is characterized at least by a location along said optical fiber link;
identifying events in said optical fiber link from return light of acquisitions performed at a second wavelength to create a second list of events wherein each event of said second list is characterized at least by a location along said optical fiber link; and
deriving a value of a parameter characterizing, at said second wavelength, an event present in said first list but missing from the second list using return light from acquisi

Assignees

• Exfo Inc

Inventors

• L Heureux Mario
• Leclerc Michel
• Thomassin Eric
• Perron Stephane

Classifications

• G01M11/3118

  using coded light-pulse sequences · CPC title

• G01M11/39

  in which light is projected from both sides of the fiber or waveguide end-face · CPC title

• G01M11/3109 Primary

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

• G01M11/3145 Primary

  Details of the optoelectronics or data analysis · CPC title