Arc recentering

• US 20030172680A1
• Filed: 03/11/2003
• Published: 09/18/2003
• Est. Priority Date: 05/09/2000
• Status: Active Grant

• Current Assignee: Telefonaktienbolaget L.M. Ericsson
• Original Assignee: Telefonaktienbolaget L.M. Ericsson
• Inventors: Wallin, David, Huang, Wei-Ping, Adeback, Tomas
• Granted Patent: US 7,845,194 B2
• Time in Patent Office: Days
• US Class Current: 65/377
• CPC Class Codes: G02B 6/2551 using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch

Abstract

In splicing two optical fibers to each other using an electric arc formed between electrodes images of the regions being heated and thereby fusioned to each other are taken. The images cover a rectangular field (43) having the fibers located centrally, along a center line of the field and parallel to the long sides of the field. The images are evaluated to determine a value of the position of the center of the electric arc in relation to the position of the end surfaces of the fibers. This value can then be used for placing the end surfaces just at the arc center. In the image the image of the optical fibers can be excluded so that only light intensity from the air discharge of the electric arc is recorded in the captured images. The field (41) excluded can be a narrow strip of uniform width located symmetrically around the image of the fibers. Using such a repositioning of the end surfaces of the fibers results in splices which are substantially equal to each other and thus a well repeatable splicing process is obtained.

Claims

1. A method of splicing two optical fibers, a left fiber and a right fiber, to each other, the method comprising the successive steps of:

placing the two optical fibers having their end regions aligned with each other and their end surfaces at or in close contact with each other,

supplying electric voltage to electrodes to produce an electric arc between points of the electrodes, the electric arc heating regions of the two optical fibers at the end surfaces to fusion material of the two optical fibers at the end surfaces together to give a splice,

stopping the energizing of the electrodes and making the heated regions cool,

characterized in that in the step of energizing the electrodes, the following steps are successively executed;

capturing at least one image of the heated regions of the two optical fibers and of a region surrounding the heated regions,

evaluating the at least one image to determine a value of the position of the center of the electric arc in relation to the position of the end surfaces,

making at least one of;

storing the determined value,

using the determined value to modify a previous value of the position of the center of the electric arc in relation to the position of the end surfaces, and

moving the two optical fibers in relation to the electrodes in accordance with the determined value so that, when still energizing the electrodes, the center of the electric arc is located substantially centered in the end surfaces.

2. A method according to claim 1, characterized in that in evaluating the at least one image, at least one rectangular field of the image is selected having long sides parallel to the longitudinal direction of the image of the two optical fibers.

3. A method according to claim 2, characterized in that the at least one rectangular field of the image is selected to have the image of the two optical fibers located substantially centrally in the field.

4. A method according to claim 2, characterized in that the at least one rectangular field of the image is selected not to include the image of the two optical fibers.

5. A method according to claim 4, characterized in that the at least one rectangular field of the image is selected to comprise two fields, each field not including the image of the two optical fibers and the fields being located symmetrically at the two sides of the image of the two optical fibers.

6. A method according to claim 2, characterized in that the at least one rectangular field of the image is selected not to include the image of the cores of the two optical fibers.

7. A method according to claim 6, characterized in that the at least one rectangular field of the image is selected to comprise two fields, each field not including the image of the cores of the two optical fibers and the fields being located symmetrically at the two sides of the two optical fibers.

8. A method according to claim 2, characterized in that in evaluating the at least one image, in the at least one rectangular field total light intensity values are determined for consecutive values equally spaced in a direction along the long sides of the field.

9. A method according to claim 8, characterized in that a smooth curve is fitted to the determined light intensity values and that the position of a maximum of the smooth curve is taken to be a value of the position of the center of the arc.

10. A method according to claim 9, characterized in that the curve is the sum of a Gaussian and a constant.

11. Apparatus for splicing two optical fibers to each other comprising:

aligning clamps for holding and placing the two optical fibers to have their end regions aligned with each other and their end surfaces at or in close contact with each other,

electrodes for producing an electric arc between points of the electrodes, the electric arc heating regions of the two optical fibers at the end surfaces to fusion material of the two optical fibers at the end surfaces together to give a splice,

an imaging system for capturing pictures of the end regions of the optical fibers,

control means connected to the aligning clamps for performing alignment movements, to the electrodes for energizing the electrodes, and to the imaging system for commanding when pictures are to be taken,

characterized in that the imaging system comprises;

image capturing means for capturing images of the splice regions of two optical fibers held by the aligning clamps,

evaluating means connected to the image capturing means for evaluating images captured by the image capturing means to determine a value of the position of the center of the electric arc in relation to the position of the end surfaces,

the control means being arranged to make at least one of;

storing the determined value in predetermined storing means,

using the determined value to modify a previous value of the position of the center of the electric arc in relation to the position of the end surfaces, and

controlling the aligning clamps to move the two optical fibers in relation to the electrodes in accordance with the determined value so that, when still energizing the electrodes, the center of the electric arc is located substantially centered in the end surfaces.

12. Apparatus according to claim 11, characterized in that the evaluating means comprise field selecting means for selecting from an image captured by the image capturing means, at least one rectangular field having long sides parallel to the longitudinal axes of the images of the two optical fibers in the captured image, the evaluating means using only the selected at least one field in determining a value of the position of the center of the arc.

13. Apparatus according to claim 12, characterized in that the field selecting means are arranged to select the at least one rectangular field to have the image of the two optical fibers located substantially centrally in the field.

14. Apparatus according to claim 12, characterized in that the field selecting means are arranged to select the at least one rectangular field not to include the image of the two optical fibers.

15. Apparatus according to claim 14, characterized in that the field selecting means are arranged to select the at least one rectangular field to comprise two fields, each field not including the image of the two optical fibers and the fields being located substantially symmetrically at the two sides of the images of the two optical fibers.

16. Apparatus according to claim 12, characterized in that the field selecting means are arranged to select the at least one rectangular field not to include the image of the cores of the two optical fibers.

17. Apparatus according to claim 16, characterized in that the field selecting means are arranged to select the at least one rectangular field to comprise two fields, each field not including the image of the cores of the two optical fibers and the fields being located substantially symmetrically at the two sides of the images of the two optical fibers.

18. Apparatus according to claim 12, characterized in that the evaluating means comprise light intensity determining means for determining from the at least one image, in the at least one rectangular field total light intensity values for consecutive coordinate values equally spaced in a direction along the long sides of the field.

19. Apparatus according to claim 18, characterized in that the evaluating means comprise curve fitting means for fitting a smooth curve to light intensity values, the evaluating means arranged to take the position of a maximum of a smooth curve fitted to light intensity values of an image captured by the image capturing means to be a value of the position of the center of the arc.

20. Apparatus according to claim 19, characterized in that the curve fitting means are arranged to use as the smooth curve a sum of a Gaussian and a constant.