Optical cross connect apparatus and method
A new architecture is proposed for making optical cross connect in wavelength division multiplexed networks. The value of optical networks incorporating all-optical cross connects is typically associated with being able to selectively route individual channel wavelengths through several network nodes without performing optical-electrical and electrical-optical conversion. From a network perspective, most work on the optical cross connect architectures have been concentrated on the highest possible capability for the cross-connect itself. The problem with considering optical cross connect architectures in isolation without attention to the rest of the network may lead to unnecessarily complicated hardware. In the proposed architecture, architecture considers the network as a whole and significant cost reductions as well as complexity reductions are realized.
1. An optical cross-connect apparatus, comprising:
a plurality of optical inputs;
a plurality of optical outputs;
an optical cross-connect defining a plurality of optical cross-connect paths between said plurality of optical inputs and said plurality of optical outputs;
at least one optical filter provided outside of said cross-connect, said at least one optical filter filtering at least one optical channel of an optical signal flowing into at least one of said plurality of optical inputs or filtering at least one optical channel of an optical signal flowing out of at least one of said plurality of optical outputs or both; and
wherein at least one of said plurality of optical cross-connect paths does not have a filter within said cross-connect in optical communication therewith.
2. The optical cross-connect apparatus of claim 1 , wherein said optical cross-connect includes:
optical splitters optically coupled to said optical inputs; and
optical combiners optically coupled to said optical outputs, wherein said optical splitters are optically coupled to said optical combiners in a broadcast and combine arrangement.
3. The optical cross-connect apparatus of claim 2 , wherein each optical input is optically coupled to a respective one of said optical splitters and each optical output is optically coupled to a respective one of said optical combiners.
4. An optical cross-connect apparatus, comprising:
a plurality of optical inputs;
a plurality of optical outputs;
an optical cross-connect provided between said plurality of optical inputs and said plurality of optical outputs; and
at least one optical filter provided outside of said cross-connect, said at least one optical filter filtering at least one optical channel of an optical signal flowing into at least one of said plurality of optical inputs or filtering at least one optical channel of an optical signal flowing out of at least one of said plurality of optical outputs or both;
wherein there are no optical filters included within said optical cross-connect.
5. The optical cross-connect apparatus of claim 1 , wherein the optical cross-connect is spectrally transparent.
6. The optical cross-connect apparatus of claim 1 , wherein at least one of said plurality of optical filters is a multi-band-pass filter.
7. The optical cross-connect apparatus of claim 1 , wherein at least one of said plurality of optical filters is a reconfigurable multi-band-pass filter.
8. The optical cross-connect apparatus of claim 1 , wherein said optical cross-connect includes a plurality of optical couplers.
9. The optical cross-connect apparatus of claim 1 , wherein at least one of said plurality of optical couplers is a passive optical coupler.
10. A method of optimizing a cross-connect apparatus by reducing the number of filters required for cross connecting a plurality of optical inputs and a plurality of optical outputs, the method comprising:
providing an optical cross-connect between the plurality of optical inputs and the plurality of optical outputs;
optically filtering at least one optical channel of an optical signal flowing into at least one of said plurality of optical inputs or at least one optical channel of an optical signal flowing out of at least one of said plurality of optical outputs or both, thereby obviating the requirement of optically filtering said at least one optical channel within said optical cross-connect; and
providing a signal from said at least one optical input to at least one optical output without filtering said signal within said optical cross-connect.
11. The method of claim 10 , further including the steps of providing a signal from each of said plurality of optical inputs to each of said plurality of optical outputs without filtering any of said signals within said optical cross-connect.
12. The method of claim 10 , wherein said optically filtering step includes multi-band-pass filtering at least one optical channel of an optical signal flowing into at least one of said plurality of optical inputs or at least one optical channel of an optical signal flowing out of at least one of said plurality of optical outputs or both.
13. An optical cross-connect apparatus, comprising:
a plurality of optical inputs;
a plurality of optical outputs;
an optical cross-connect provided between said plurality of optical inputs and said plurality of optical outputs such that paths are formed between a subset of said plurality of optical inputs and a subset of said plurality of optical outputs, wherein a path is defined as a connection between a particular optical input and a particular output;
at least one optical filter provided outside of said cross-connect such that for each one path that exists between a particular optical input and a particular optical output, the path's input is filtered or the path's output is filtered or both; and
wherein at least one of said paths does not have a filter within said cross-connect in optical communication therewith.
14. The optical cross-connect apparatus of claim 13 , wherein said optical cross-connect includes:
optical splitters optically coupled to said optical inputs; and
optical combiners optically coupled to said optical outputs, wherein said optical splitters are optically coupled to said optical combiners in a broadcast and combine arrangement.
15. The optical cross-connect apparatus of claim 14 , wherein each optical input is optically coupled to a respective one of said optical splitters and each optical output is optically coupled to a respective one of said optical combiners.
16. The optical cross-connect apparatus of claim 13 , wherein there are no optical filters included within said optical cross-connect.
17. The optical cross-connect apparatus of claim 13 , wherein substantially all of the paths do not have a filter within said cross-connect in optical communication therewith.
18. The optical cross connect apparatus of claim 13 , wherein each path is filtered and the total number of filters is equal to twice the number of paths.
19. The optical cross connect apparatus of claim 13 , wherein there are N paths, wherein each path is filtered and wherein the total number of filters is less than N*(N−1).
20. A fiber ring network, comprising:
a first and second outer rings carrying optical signals in a first direction;
a first and second inner rings carrying optical signals in a second direction opposite the first direction;
an optical cross-connect apparatus as claimed in claim 1 for providing for at least an outer-to-outer connection between the first and second outer rings and an inner-to-inner connection between said first and second inner rings; and
wherein there are no optical filters within said optical cross-connect apparatus, said network further comprising at least one adjacent ring node optically placed in a path of one or more of said first and second outer rings and first and second inner rings such that said adjacent ring node performs an optical filtering function.
21. The fiber ring network of claim 20 , wherein said adjacent ring node includes a multi-band-pass filter.
22. A mesh network, comprising:
an optical cross-connect apparatus as claimed in claim 1 ; and
an optical add/drop module optically connected to one of said plurality of optical inputs and to one of said plurality of optical outputs.
23. The mesh network of claim 22 , wherein the optical add/drop module includes a first and second multi-band-pass filters.
24. The mesh network of claim 23 , said first and second multi-band-pass filters are optically connected to said one of said plurality of optical inputs and to said one of the plurality of said optical outputs, respectively.
25. The optical cross-connect apparatus of claim 13 , wherein each path has a unique optical input filter and optical output filter filtering only that path.
26. The optical cross-connect apparatus of claim 2 , wherein there are no optical filters within the optical coupling between said optical splitters and said optical combiners.