Optical backplane interconnect

Details Optical backplane interconnect Optical backplane interconnect

1996-09-23

1998-08-11

Sanghavi, Hemang

Optical waveguides

Accessories

Splice box and surplus fiber storage/trays/organizers/ carriers

385134, 385 24, 385 42, G02B 600

Patent

active

057939195

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to an optical backplane interconnect that has particular but not exclusive application to optical telecommunication networks.


BACKGROUND

In order to connect all the nodes of a network to one another, a large number of connections is usually required, which becomes impractical if individual optical fibres are used to make the connections. In order to simplify the node connections, an optical bus architecture has been proposed in "Optical Interconnect based on a Fibre Bus" F. MacKenzie et al--Optical and Quantum Electronics 24 (1992) S 491-S 504. This discloses an optical bus consisting of a plurality of parallel D-section optical fibres. Connections are made to the optical fibres by means of further D-section fibres that overlay the fibres of the bus at a predetermined angle. As explained in the paper, the angle of intersection determines the degree of coupling between the fibres and the arrangement permits signals to be selectively coupled into and from the bus. The connections can be arranged in groups, to provide a modular structure. The circuitry is arranged on separate cards that carry both optical and electrical circuits, which are connected to the optical fibre bus and the cards can be arranged in a racked arrangement in a similar manner to conventional electrical printed circuit boards in a telephone exchange. Reference is also directed to EP-A-0382430 which shows a similar arrangement.
However, problems have been encountered in designing an interconnect which provides a consistent and reliable coupling to the optical fibre bus and as a result, when cards are removed and reinserted, or inserted in different locations in the rack, the optical coupling to the bus may change undesirably.
The present invention seeks to overcome these problems.


SUMMARY OF THE INVENTION

In accordance with the present invention there is provided an optical backplane interconnect comprising: a backplane including a plurality of optical bus waveguides; a connecting block provided with a plurality of optical paths to be aligned in a predetermined angular relationship with the bus waveguides of the backplane so as to form optical couplings therewith; and characterised by coupling means operative in such a manner that as the connecting block is moved in a forward direction towards the backplane, the block is caused automatically to shift laterally of said forward direction so as to produce self-alignment of the waveguides and the paths in said predetermined angular relationship.
The interconnect may include a card, a support on which the backplane is mounted, and mounting means on the support for the card, the coupling means being resiliently mounted on the card and operative so that as the card is moved in the forward direction into the mounting means the connecting block moves relative to the card to produce said self alignment.
The backplane may include a plurality of D-section optical fibres which in the region of the connecting block are generally parallel to one another, and the optical paths in the connecting block may include portions that are generally parallel and spaced for coupling with respective ones of the optical fibres, said coupling means holding the optical path portions at a predetermined angle relative to the optical fibres.
The card can carry optical components connected to said plurality of optical paths. The optical paths may themselves be defined by further D-section optical fibres. The coupling means may comprise a groove in the backplane and projection means on the connecting block, that fits into the groove. The projection means may comprise an elongate member that runs longitudinally of the groove, so as to hold the connecting block at a predetermined angle to the backplane. Alternatively, the projection means may comprise one or more spaced members that fit into the groove. The or each spaced member may comprise a ball received in a recess in the connecting block.
In an alternative configuration, the channel in the backplane may be wider than the

REFERENCES:
patent: 4533208 (1985-08-01), Stowe
patent: 4943136 (1990-07-01), Popoff
patent: 5596662 (1997-01-01), Boscher
MacKenzie et al, "Dichroic Tap For Optical Multiple Access Systems with Distributed Amplification", Electronics Letters, 17th Jan. 1991, vol. 27, No. 2, pp. 181-183.
Sakakibara et al, "A Slotted Aloha With Multiple Common Receivers Over AWGN Rayleigh-Fading Channels", IEEE, 1989, pp. 0418-0422 No Month Available.
MacKenzie et al, Optical Interconnect Based on a Fibre Bus, Optical and Quantum Electronics, 24 (1992), pp. S491-S-504 No Month Available.

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