Optical fiber interconnections using self-aligned core-extensions

• US 5,515,464 A
• Filed: 11/22/1993
• Issued: 05/07/1996
• Est. Priority Date: 07/06/1992
• Status: Expired due to Fees

• Current Assignee: Sang K. Sheem
• Original Assignee: Sang K. Sheem
• Inventors: Sheem, Sang K.
• Primary Examiner(s): Healy, Brian
• Application Number:
  US08/155,553
• Time in Patent Office: 897 Days
• Field of Search: 385/14, 385/15, 385/31, 385/43, 385/49, 385/50, 385/129, 385/130, 385/131, 385/132, 385/39, 385/51, 385/52, 385/33
• US Class Current: 385/49
• CPC Class Codes: G02B 6/2808 using a mixing element which evenly distributes an input signal over a number of outputs
• CPC Class Codes: G02B 6/2817 using reflective elements to split or combine optical signals
• CPC Class Codes: G02B 6/2848 having refractive means, e.g. imaging elements between light guides as splitting, branching and/or combining devices, e.g. lenses, holograms
• CPC Class Codes: G02B 6/305 and having an integrated mode-size expanding section, e.g. tapered waveguide

Abstract

An optical fiber interconnecting structure for connecting an optical fiber to an optical channel waveguide, in which a channel waveguide is extended collinearly by a hollow channel with sectional area and shape substantially identical to those for the channel waveguide. An optical fiber is laid collinearly with the channel, and a core-extension is formed at the end facet of the optical fiber to form a gradual and smooth optical transition to the channel waveguide. The channel waveguide may be tapered out to have a substantially larger sectional area at the far end so as to ease the optical interconnection.

Claims

1. An optical fiber interconnecting structure for connecting an optical fiber to an optical channel waveguide, comprising:

a hollow channel fabricated in an optical substrate;

a channel waveguide fabricated in the same optical substrate, and laid collinearly as an extension of the hollow channel, with the cross-sectional shape and area substantially identical to those of the hollow channel;

an optical fiber with a core and a cladding, laid collinearly in the hollow channel with its end facet facing the hollow channel; and

a core-extension of the optical fiber residing inside the hollow channel and made of a photo-reactive material, the physical characteristics of which can be altered and shaped by a photo-exposure, and built on the end facet of the core following the shape of the diverging radiation pattern of light that stretches over a distance far enough to make the maximum diameter at the farthest end substantially larger than the core diameter, so as to allow the core-extension to make a physical contact with the walls of the hollow channel, and self-aligned with the core by formation of the core-extension by said radiation pattern of the light, and further having an index of refraction greater than that of the surrounding medium so as to possess light confining function;

whereby a light leaving the core of the fiber is coupled into the channel waveguide through the core-extension with a reduced loss and the shape and size of the core-extension is transformed gradually from the shape and size of the core of the optical fiber to the shape and size of the channel waveguide in the physical connection.

2. The invention according to claim 1 wherein the hollow channel is fabricated by a photolithography technique utilizing photo-reactive material.

3. The invention according to claim 1 wherein the hollow channel is fabricated by molding technique.

4. The invention according to claim 1 wherein the channel waveguide and the core-extension are made of the same material.

5. The invention according to claim 1 wherein the core is surrounded by a cladding the thickness of which is reduced locally so as to minimize the distance between the core and the wall of the hollow channel.

7. The invention according to claim 1 wherein the fiber is entirely located outside the hollow channel, and the width and depth of the hollow channel is smaller than the diameter of the cladding and slightly larger than the diameter of the core of the optical fiber.

8. The invention according to claim 1 wherein the channel waveguide is tapered out to have a larger cross-section at a greater distance from the core-extension.

9. The invention according to claim 8 wherein the cross-section of the channel waveguide is enlarged in one dimension.

10. The invention according to claim 8 wherein the cross-section of the channel waveguide is enlarged in two dimensions.

11. The invention according to claim 8 wherein the enlarged cross-section has a square shape.

12. The invention according to claim 8 wherein the enlarged cross-section has a round shape.

13. The invention according to claim 1 wherein the optical fiber is removably placed inside the hollow channel.

22. The invention according to claim 1, wherein the divergence angle of the core-extension is substantially smaller than the maximum possible divergence angle of optical rays radiating from the core, so as to minimize the loss of a light propagating through the core-extension.

6. An optical fiber interconnecting structure for connecting an optical fiber to an optical channel waveguide comprising:

a hollow channel fabricated in an optical substrate;

a channel waveguide fabricated in the same optical substrate, and laid collinearly as an extension of the hollow channel, with the cross-sectional shape and area substantially identical to those of the hollow channel;

an optical fiber with a core and a cladding, laid collinearly with the hollow channel with its end facet facing the hollow channel; and

a core-extension of the optical fiber that resides inside the hollow channel, interconnecting the core of the optical fiber to the channel waveguide;

whereby a light may be transmitted between the core of the fiber and the channel waveguide through the core-extension; and

wherein the sectional area of the hollow channel is gradually enlarged as the distance from the channel waveguide increases, so as to ease the insertion of the optical fiber into the hollow channel.

14. An optical fiber interconnecting structure for connecting an optical fiber to an optical channel waveguide comprising:

a hollow channel fabricated in an optical substrate;

a channel waveguide fabricated in the same optical substrate, and laid collinearly as an extension of the hollow channel, with the cross-sectional shape and area substantially identical to those of the hollow channel;

an optical fiber with a core and a cladding, laid collinearly with the hollow channel with its end facet facing the hollow channel; and

a core-extension of the optical fiber that resides inside the hollow channel, interconnecting the core of the optical fiber to the channel waveguide;

whereby a light may be transmitted between the core of the fiber and the channel waveguide through the core-extension; and

wherein the optical fiber is placed inside the hollow channel and is short enough to be contained within the hollow channel so as to allow a second optical fiber to be releasably connected to the optical fiber in an end-butted fashion inside the hollow channel.

15. An arrayed optical fiber interconnecting structure for connecting an array of optical fibers to an array of optical channel waveguides in one-to-one fashion, comprising:

an array of hollow channels fabricated in an optical substrate;

an array of channel waveguides fabricated in the same optical substrate with each of the channel waveguides mated with one of the hollow channels in one-to-one fashion, and each of the channel waveguides laid collinearly as an extension of the corresponding hollow channel, with the cross sectional shape and the area of each of the channel waveguides substantially identical to the cross sectional shape and the area of the corresponding hollow channel;

an array of optical fibers with a core and a cladding, with one of the optical fibers assigned to one of the hollow channels in one-to-one fashion, with each optical fiber laid collinearly in the corresponding hollow channel with its end facet facing the corresponding hollow channel; and

an array of core-extensions of the optical fibers, with one of the core-extensions assigned to one of the optical fibers in one-to-one fashion, with each core-extension residing inside the corresponding hollow channel and made of a photo-reactive material, the physical characteristics of which can be altered and shaped by a photo-exposure, and built on the end facet of the core following the shape of the diverging radiation pattern of light that stretches over a distance far enough to make the maximum diameter at the farthest end substantially larger than the core diameter, so as to allow the core-extension to make a physical contact with the walls of the hollow channel, and self-aligned with the core by formation of the core-extension by said radiation pattern of the light, and further having an index of refraction greater than that of the surrounding medium so as to possess light confining function;

whereby a light leaving the core of any of the optical fibers is coupled into the corresponding channel waveguide through the corresponding core-extension with a reduced loss and the shape and size of the core-extension is transformed gradually from the shame and size of the core of the optical fiber to the shape and size of the channel waveguide in the physical connection.

16. The invention according to claim 15 wherein the hollow channels are fabricated by a photolithography technique utilizing photo-reactive material.

17. The invention according to claim 15 wherein the hollow channels are fabricated by molding technique.

18. The invention according to claim 15 wherein the channel waveguides have evanescent-field coupling with neighboring channel waveguides.

19. The invention according to claim 15 wherein the channel waveguides are tapered out in the width so as to merge with the neighboring channel waveguides for optical coupling.

20. The invention according to claim 15 wherein the channel waveguides are tapered out to have a larger cross-section at a greater distance from the core-extensions, but still separated from the neighboring channel waveguides.

21. The invention according to claim 20 wherein the ends of the tapered channel waveguides are terminated by one common end facet that is substantially orthogonal to the orientation of the channel waveguides, so as to form a demountable end-butt light connection interface with another optical components.