Browse Prior Art Database

Optical Wiring Using Holographic Beam Deflection

IP.com Disclosure Number: IPCOM000035729D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 6 page(s) / 103K

Publishing Venue

IBM

Related People

Berstis, V: AUTHOR [+3]

Abstract

Disclosed is a circuit interconnection method based on holographically directed optical light beams traveling through air or other linear medium with no bottlenecks in the optical path.

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Optical Wiring Using Holographic Beam Deflection

Disclosed is a circuit interconnection method based on holographically directed optical light beams traveling through air or other linear medium with no bottlenecks in the optical path.

Currently systems, such as the IBM 3090, are based upon TCM (Thermal Conduction Module) packaging methods. A TCM is a multilayer ceramic substrate containing multiple wiring plane pairs where one plane of the pair is dedicated to wiring in the horizontal and the other in the vertical direction. Interconnection among the plane pairs is implemented with "vias" which pass through the layers. Integrated circuit chips are placed in a regular rectangular arrangement on the surface of the TCM. Connection are made between the chips and the TCM's surface using melted solder balls.

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When the chip pin count and number of chips increase, it becomes more difficult to place the chips and route their interconnections through the wiring planes. These difficulties include wiring congestion, keeping wire length within given bounds, and other factors such as topological constraints affecting transmission characteristics (wiring rules) and crosstalk noise. Larger systems exceed the limit of the wiring capability of current TCM technology, despite the large number of wiring layers.

This disclosure describes a method for relieving many of the wiring congestion problems associated with current TCM technology. The approach relieves the wiring bottleneck by optically realizing the more distant connections on the package while continuing to use the existing TCM wiring technology for local (short) connections. The optical signals pass from the source chip 1 (Fig. 1) through a via 2 to the other TCM surface connecting to a laser diode 3. The laser diode generates a monochromatic and coherent light beam 4 of known wavelength and intensity. This permits the beam to be easily directed to the destination by using a holographic plate 5 in front of the laser diode. The receiver of the beam consists of a suitable transducer 6 (photodiode or phototransistor) by which the optical beam is converted back to an electrical signal, which is passed through a TCM via to the receiving chip. The receiving photodiode also has a holographic plate 7 in front of it to maximize signals coming only from the intended source laser.

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The optical connections lend themselves to a variety of packaging configurations. One such configuration is to have a mirror 1 (Fig. 2) some distance from the optical side of the TCM, where all of the optical signals bounce off the mirror back to the TCM. This approach is useful for relieving global wiring congestion in smaller systems. Fig. 1 detailed a configuration where two TCMs (perhaps smaller in size than the original) have their optical sides facing each other. Thus, optical paths are used for connections between the two TCMs but not within individual TCMs. A modification to this configu...