Protected optical switching matrix

Details Protected optical switching matrix Protected optical switching matrix

1999-04-15

2001-12-25

Henry, Jon (Department: 2872)

Optical waveguides

With optical coupler

Switch

C359S199200

Reexamination Certificate

active

06334010

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention concerns a protected optical switching matrix which can be used in particular as a cross connect switch for optical links.
A prior art high capacity optical switching matrix has been made from an array of lower capacity optical switches. The switches can all be of the space switching type, all of the spectral switching type or a combination of the two types.
To protect a matrix of the above kind, i.e. to keep it working without loss of capacity if any of the switches fails, duplicating each stage of the network with an identical stage that is not normally used, but which is used in place of the stage that has failed if any of the switches constituting it fails, is known per se. A protection system of the above kind is based on so-called 1 for 1 redundancy, in other words one redundant unit for each working unit. Its main drawback is that it doubles the cost of the matrix.
A protected matrix can also be modified to increase its capacity by adding matrix units without interrupting service.
In the prior art there are various architectures for an optical switching matrix:
A first prior art architecture includes a plurality of spatial switching matrix units connected in cascade, using the Clos architecture, for example. The drawbacks of this type of matrix are:
High insertion losses, which cannot be compensated simultaneously in both of the ranges of optical wavelengths routinely used: 1 300 nm and 1 550 nm. This limits the maximum size of the optical matrices that can be made using this architecture.
Protecting the matrix necessarily entails the use of 1 for 1 redundancy for the entire matrix, which is costly.
The number of matrix units that must connected in cascade is high, leading to high cost.
A second prior architecture includes a plurality of spectral switching matrix units or a combination of spatial switching matrix units and spectral switching matrix units. This latter combination can produce a large matrix but the second architecture also has the disadvantage of necessitating 1 for 1 redundancy for the entire matrix if it is to be protected.
SUMMARY OF THE INVENTION
The aim of the invention is to propose a protected optical matrix that is less costly to implement.
The invention consists in a protected optical switch matrix having N inputs and N outputs and including an optical switching fabric, an input interface performing wavelength conversion and an output interface performing wavelength filtering, characterized in that the input interface and the output interface are protected by redundancy provided by r redundant units for E working units where r is a number very much less than E.
The matrix so characterized is less costly than a prior art protected matrix because the cost of the input and output interfaces is increased only in the proportion r/E rather than doubled.
In a first embodiment the input interface includes at least one group of E working wavelength converters and r redundant converters which are all tuned permanently to the same wavelength.
In a second embodiment the input interface includes at least one group of E working wavelength converters and r redundant converters which can all be tuned in the same band of wavelengths.
In a third embodiment the input interface includes at least one group of E working wavelength converters which are all tuned permanently to E respective different wavelengths and r redundant converters which can all be tuned to any one of those E wavelengths.
In a fourth embodiment the output interface includes at least one group of E working wavelength filters and r redundant converters which can all be tuned to the same range of wavelengths.
In a fifth embodiment the output interface includes at least one group of E working wavelength filters and r redundant converters which are all tuned permanently to the same wavelength.
In a sixth embodiment the output interface includes at least one group of E working wavelength filters which are all tuned permanently to E respective different wavelengths and r redundant converters which can all be tuned to any one of those E wavelengths.


REFERENCES:
patent: 5208691 (1993-05-01), Nishio
patent: 5671304 (1997-09-01), Duguay
patent: 5754320 (1998-05-01), Watanabe et al.

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