Free-Space Optical Interconnect With Asymmetric Light Pipes

• US 20100028018A1
• Filed: 10/31/2008
• Published: 02/04/2010
• Est. Priority Date: 08/01/2008
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Mathai, Sagi, Tan, Michael, Rosenberg, Paul
• Granted Patent: US 8,275,266 B2
• Time in Patent Office: Days
• US Class Current: 398/141
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/43 Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections
• CPC Class Codes: H04B 10/803 Free space interconnects, e.g. between circuit boards or chips

Abstract

An optical interconnect system includes components such as circuit boards, server blades, or a backplane with respective light pipes for an optical signal. The light pipe in a component transmitting the optical signal receives a collimated beam and directs the collimated beam for transmission. The light pipe in a receiving component is nominally aligned with the light pipe pf the transmitting component and separated from the first light pipe by free space. The light pipe on the receiving side is larger than the light pipe on the transmitting side and can therefore accommodate an expected alignment error.

Claims

1. An optical interconnect system comprising:

a first component including a first light pipe positioned to receive a collimated optical signal beam and to direct the collimated optical signal beam for transmission from the first component, the first light pipe having a cross-section of a first size; and

a second component including a second light pipe nominally aligned with the first light pipe and separated from the first light pipe by a free-space gap, wherein the second light pipe has a cross-section of a second size that is larger than the first size.

2. The system of claim 1, wherein the second size is larger than the first size by a margin that is large enough to accommodate expected error in alignment of the second light pipe with the first light pipe.

3. The system of claim 2, further comprising a mechanical alignment system that couples the first light pipe to the second light pipe and controls the expected error in alignment.

4. The system of claim 1, wherein the first component further comprises:

an optical transmitter, and

a collimating lens positioned to collimate an optical signal from the optical transmitter to produce the collimated optical signal beam.

5. The system of claim 1, wherein:

the first component further comprises a plurality of first light pipes having cross-sections of the first size and being positioned to respectively receive a plurality of collimated optical signals for transmission from the first component; and

the second component further comprises a plurality of second light pipes having cross-sections of the second size and respectively being aligned with the first light pipes.

6. The system of claim 5, wherein:

the first component further comprises a plurality of third light pipes having cross-sections of the second size; and

the second component further comprises a plurality of fourth light pipes having cross-sections of the first size and being positioned to respectively receive a plurality of collimated optical signals for transmission from the second component, the fourth light pipes being respectively aligned with the third light pipes.

7. The system of claim 6, wherein the first light pipes and the third light pipes extend through a block.

8. The system of claim 1, wherein the first light pipe comprises a hollow tube having reflective walls.

9. The system of claim 1, further comprising turning optics positioned in the free space gap, wherein the second light pipe is aligned so that the collimated optical signal after exiting the first light pipe and being redirected by the turning optics enters the second light pipe.

10. The system of claim 1, wherein the first component comprises a first blade in a server system.

11. The system of claim 10, wherein the second component comprises a second blade in the server system.

12. The system of claim 10, wherein the second system comprises a backplane of the server system.

13. A method for transmitting information comprising:

collimating an optical signal representing the information;

directing the optical signal after collimation into a first light pipe having a cross-section of a first size;

aligning a second light pipe with the first light pipe, wherein the aligning has an expected alignment error, and the second light pipe has a cross-section of a second size that is larger than the first size by a margin that accommodates the expected alignment error; and

receiving the optical signal through the second light.

14. The method of claim 13, wherein the optical signal traverses a free-space gap between the first light pipe and the second light pipe.

15. The method of claim 14, further comprising reflecting the optical signal using a turning mirror in the free-space gap, wherein the second light pipe is aligned to receive the optical signal after reflection from the turning mirror.