Deformable Optical Interconnect Light Guide
Original Publication Date: 2001-May-21
Included in the Prior Art Database: 2001-May-21
James K. Gehrke: AUTHOR [+3]
AbstractDeformable Optical Interconnect Light Guide
DEFORMABLE OPTICAL INTERCONNECT LIGHT GUIDE
By James K. Gehrke Daniel R. Schroeder Robert R. Kornowski
Others have previously described the use of a notched light guide to communicate between cards in a card cage. Emitters and receptors would be contained within each plug-in card, and would be coupled to an external light guide to allow the cards to transmit and receive modulated light to and from other cards. The issues with the use of a notched light guide are:
1) The notches that support optical coupling to the light guide must be placed at specific locations along the pipe. This limits the future flexibility of card size and location along the pipe. 2) The fixed position of the notches forces tight mechanical tolerancing to optimally couple the optical devices in the plug-in cards to the light guide. 3) There is potential for dirt or moisture to get trapped between the light guide and the optical devices in the card, reducing the light coupling to inadequate levels.
This publication describes how the use of a deformable optical light guide would help resolve these problems.
Principle of Operation
It is proposed to use a flexible, deformable light guide, possibly of an elastomeric material, although other materials may be suitable. During insertion of the plug-in card, the light guide is displaced in some manner, with the displacement providing optical coupling between the optical emitters/receptors and the light guide. After insertion, there is intimate contact between the emitters/receptors and the light guide. Several different methods are proposed in the attachment, each addressing some or all of the issues listed above.
Because the light guide can be displaced by the emitters/receptors anywhere along its length, mounting flexibility is supported and mechanical tolerancing issues are minimized. Because the displacement process produces intimate contact between the light guide and emitters/receptors, degradation due to foreign material in the optical path is minimized.
Method 1 – Optical device directly displaces the light guide
When the card is inserted into the card cage, the emitter/receptor deforms the light guide and allows light to be transmitted or received in the lightpipe. This method effectively solves all three of the previously noted issues. The light guide material must be readily deformable and retain that property for the life of the product. If the refractive index of the light guide is higher than that of the emitter/receptor, the light will more effectively be bent in a direction parallel to the axis of the light guide. It may be necessary to paint or in some way coat the side of the light guide opposite the emitter/receptor to aid in capturing the emitted light within the light guide. For example, the support member shown above the light guide could be painted white.
A spherical shape is shown for the emitter/receptor. Other shapes, for example a c...