What is claimed is:
1. A method of forming an optical fiber preform, the method comprising:
providing a consolidated glass preform precursor body having an outer surface;
depositing a layer of silica soot onto the outer surface of the consolidated glass preform precursor body to form a composite preform comprised of a consolidated glass portion and a silica soot portion; and
in a deuterium-exposing step, exposing the composite preform to an atmosphere containing a concentration of a deuterium compound for a time and at a temperature sufficient to cause the deuterium compound to penetrate the consolidated glass portion without pervading the entire glass portion.
2. The method of claim 1 wherein the depositing step further comprises causing a hydrogen compound to penetrate the consolidated glass preform precursor body.
3. The method of claim 2 wherein at least a portion of the hydrogen compound in the consolidated glass preform precursor body is exchanged with at least a portion of the deuterium compound.
4. The method of claim 1 further comprising, after the depositing step, exposing the composite preform to a chlorine-compound-containing atmosphere.
5. The method of claim 4 wherein the chlorine-compound-containing atmosphere comprises an inert gas.
6. The method of claim 4 wherein, the composite preform is exposed to a chlorine-compound-containing atmosphere prior to the deuterium-exposing step.
7. The method of claim 4 wherein the composite preform is exposed to a purge atmosphere comprising an inert gas prior to the deuterium-exposing step.
8. The method of claim 4 wherein the composite preform is exposed to a chlorine-compound-containing atmosphere, and then the composite preform is exposed to a purge atmosphere comprising an inert gas, prior to the deuterium-exposing step.
9. The method of claim 4 wherein the composite preform is exposed to a purge atmosphere comprising an inert gas after the deuterium-exposing step.
10. The method of claim 4 wherein the composite preform is exposed to a chlorine-compound-containing atmosphere after the deuterium-exposing step.
11. The method of claim 4 wherein, after the deuterium-exposing step, the composite preform is exposed to a purge atmosphere comprising an inert gas, and then the composite preform is exposed to a chlorine-compound-containing atmosphere.
12. The method of claim 1 further comprising consolidating the silica soot portion to form a second consolidated glass preform precursor body comprised of the glass portion and a second glass portion formed from the silica soot portion.
13. The method of claim 12 further comprising repeating the depositing step and the deuterium-exposing step.
14. The method of claim 13 further comprising heating and drawing the second consolidated glass preform precursor body to a reduced diameter prior to depositing silica soot thereon.
15. The method of claim 1 wherein the deuterium compound penetrates the glass portion to a desired depth.
16. The method of claim 1 wherein the consolidated glass preform precursor body is generally cylindrical about a centerline axis, wherein at least a portion of the consolidated glass preform precursor body has a radial thickness RC1 measured from the centerline axis, and wherein less than 0.1 ppm of any deuterium compound is present at radii less than about 0.25 RC1.
17. The method of claim 1 wherein less than 0.1 ppm deuterium compound is formed by the reaction of deuterium with the consolidated glass portion at radii less than about one-fourth the radius of the consolidated glass preform precursor body.
18. The method of claim 16 wherein less than 0.1 ppm of the deuterium compound is present at radii less than about 0.5 RC1.
19. The method of claim 16 wherein less than 0.1 ppm of the deuterium compound is present at radii less than about 0.75 RC1.
20. An optical fiber preform made in accordance with the method of claim 1.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of aligning images comprising:
sampling a first image and a second image, obtaining a plurality of joint feature pairs;
computing a minimum entropic graph using the joint feature pairs;
measuring the total length of the minimum entropic graph using a distance measure, obtaining a dissimilarity measure; and
minimizing the dissimilarity measure for updating the geometric transformation;
wherein computing a minimum entropic graph comprises computing a minimum spanning tree; and
wherein computing a minimum spanning tree comprises:
computing the Delaunay triangulation of a point set, obtaining a Delaunay triangulation edge set; and
computing the minimum spanning tree using the Delaunay triangulation edge set and Kruskal’s algorithm.
2. A computer readable medium embodying instructions executable by a processor to perform a method of aligning images comprising:
sampling a first image and a second image, obtaining a plurality of joint feature pairs;
computing a minimum entropic graph using the joint feature pairs;
measuring the total length of the minimum entropic graph using a distance measure, obtaining a dissimilarity measure; and
minimizing the dissimilarity measure for updating the geometric transformation;
wherein the joint feature pairs are joint feature pairs in a higher-dimensional feature space, wherein computing a minimum entropic graph comprises computing a minimum spanning tree and wherein computing a minimum spanning tree comprises:
computing the Delaunay triangulation in a reduced-dimensional feature space, wherein the reduced-dimensional feature space is obtained by projection, obtaining a triangulation; and
computing the minimum spanning tree of the triangulation in the higher-dimensional feature space.
3. A computer readable medium including computer code for aligning images executable by a processor to perform a method of aligning images, the computer readable medium comprising:
computer code for sampling a first image and a second image for obtaining a plurality of joint feature pairs;
computer code for computing a minimum entropic graph using the joint feature pairs;
computer code for measuring the total length of the minimum entropic graph using a distance measure for obtaining a dissimilarity measure; and
computer code for minimizing the dissimilarity measure for updating the geometric transformation;
wherein computing a minimum entropic graph comprises computing a minimum spanning tree and
wherein computer code for computing a minimum spanning tree comprises:
computer code for computing the Delaunay triangulation of a point set, obtaining a Delaunay triangulation edge set; and
computer code for computing the minimum spanning tree using the Delaunay triangulation edge set and Kruskal’s algorithm.
4. The computer readable medium of claim 3, wherein the computer code for minimizing the dissimilarity measure for updating the geometric transformation comprises:
computer code for estimating a gradient of the dissimilarity measure with respect to at least one parameter of a geometric transformation; and
computer code for using the gradient of the dissimilarity measure to update the geometric transformation.