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In today's reconfigurable optical add/drop multiplexer (ROADM) based optical node, ROADMs multiplex (and demultiplex) colored optical signals to form wavelength-division multiplexed (WDM) signals. Transponders connected to the ROADMs' add/drop ports convert noncolored optical signals to colored opti

In today's reconfigurable optical add/drop multiplexer (ROADM) based optical node, ROADMs multiplex (and demultiplex) colored optical signals to form wavelength-division multiplexed (WDM) signals. Transponders connected to the ROADMs' add/drop ports convert noncolored optical signals to colored optical signals (and vice versa). Dedicating transponders to given ports degrades the node's ability to route around network failures. Example embodiments of the invention include an optical node and corresponding method for routing optical signals within an optical node that compensate for this inflexibility. The optical node may include two ROADMs to transmit respective WDM signals onto at least two internode network paths and a routing module that can direct channels of the same wavelength along different internode network paths. Advantageously, a transponder may transmit (receive) different signals at the same wavelength to (from) different network node interfaces within the optical node, thereby improving the optical node's ability to route around network failures.

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1. An optical node, comprising: at least two reconfigurable optical add/drop multiplexers (ROADMs) configured to transmit or receive respective wavelength division multiplexed (WDM) signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode netw

1. An optical node, comprising: at least two reconfigurable optical add/drop multiplexers (ROADMs) configured to transmit or receive respective wavelength division multiplexed (WDM) signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths; anda routing module, coupled to at least a subset of the at least two ROADMs, configured to direct distinct signals of the same wavelength, simultaneously, to different internode network paths;wherein each ROADM includes a wavelength-selective switch (WSS), wherein a signal to be added is directed to a WSS from an add/drop port via an intranode network path, and wherein a signal received at a ROADM via an internode network path is directed via an optical path to a respective WSS on another ROADM. 2. The optical node of claim 1, wherein each ROADM includes a wavelength-selective switch (WSS), and wherein a signal to be added is directed to a WSS from an add/drop port via intranode network paths. 3. The optical node of claim 1, wherein each ROADM includes a wavelength-selective switch (WSS), and wherein a signal received at a first ROADM via an internode network path is directed via an optical path to a respective WSS on another ROADM. 4. The optical node of claim 1, wherein the optical node includes multiple routing modules, coupled to the at least a subset of the at least two ROADMs, and wherein a routing module, among the multiple routing modules, includes at least one expansion port to couple at least one ROADM, of the subset of ROADMs, optically to at least one other routing modules. 5. The optical node of claim 1, wherein at least two reconfigurable optical add/drop multiplexers (ROADMs) are configured to transmit and receive respective wavelength division multiplexed (WDM) signals. 6. An optical node, comprising: at least two reconfigurable optical add/drop multiplexers (ROADMs) configured to transmit or receive respective wavelength division multiplexed (WDM) signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths; anda routing module, coupled to at least a subset of the at least two ROADMs, configured to direct distinct signals of the same wavelength, simultaneously, to different internode network paths;wherein the routing module includes:an add component optically coupled to a bank of add ports and configured to direct add signals to the at least a subset of the at least two ROADMs; anda drop component optically coupled to a bank of drop ports and configured to direct drop signals to drop ports among the bank of drop ports. 7. The optical node of claim 6, wherein the drop component includes or is coupled to a bank of tunable filters. 8. An optical node, comprising: at least two reconfigurable optical add/drop multiplexers (ROADMs) configured to transmit or receive respective wavelength division multiplexed (WDM) signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths; anda routing module, coupled to at least a subset of the at least two ROADMs, configured to direct distinct signals of the same wavelength, simultaneously, to different internode network paths;wherein the routing module is a colorless routing module including colorless add/drop ports. 9. An optical node, comprising: at least two reconfigurable optical add/drop multiplexers (ROADMs) configured to transmit or receive respective wavelength division multiplexed (WDM) signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths; anda routing module, coupled to at least a subset of the at least two ROADMs, configured to direct distinct signals of the same wavelength, simultaneously, to different internode network paths;wherein the routing module includes (i) at least one multicast switch configured to route any drop signal to at least one drop port and (ii) at least one aggregator switch configured to route any add signal to at least one ROADM. 10. The optical node of claim 9, wherein the routing module further includes at least one tunable filter configured to filter signals directed to the at least one drop port. 11. The optical node of claim 10, wherein the routing module further includes at least one optical amplifier configured to amplify signals directed to the at least one drop port. 12. The optical node of claim 9, wherein the routing module further includes optical amplifiers configured to amplify output signals of the at least one aggregator switch. 13. An optical node, comprising: at least two reconfigurable optical add/drop multiplexers (ROADMs) configured to transmit or receive respective wavelength division multiplexed (WDM) signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths; anda routing module, coupled to at least a subset of the at least two ROADMs, configured to direct distinct signals of the same wavelength, simultaneously, to different internode network paths;wherein the optical node includes multiple routing modules, coupled to the at least a subset of the at least two ROADMs, and a distribution module optically coupling the at least two ROADMs to the multiple routing modules. 14. The optical node of claim 13, wherein the at least two ROADMs are coupled to the distribution module via corresponding add/drop ports. 15. The optical node of claim 13, wherein the at least two ROADMs are coupled to the distribution module via corresponding express ports. 16. A method of routing wavelength division multiplexed (WDM) signals, comprising: transmitting or receiving WDM signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths using at least two reconfigurable optical add/drop multiplexers (ROADMs); anddirecting, by a routing module coupled to at least a subset of the at least two ROADMs, signals to different internode network paths, simultaneously, the directed signals include distinct signals of the same wavelength;wherein directing signals includes directing a signal to be added to a wavelength-selective switch (WSS) in a ROADM from an add/drop port via an optical intranode network path to a WSS on another ROADM. 17. The method of claim 16, wherein directing signals includes directing a signal to be added to a wavelength-selective switch (WSS) in one of the at least two ROADMs from add/drop port via intranode network paths. 18. The method of claim 16, wherein directing signals includes directing signals received at a ROADM via an internode network path to a wavelength-selective switch on another ROADM via optical paths. 19. The method of claim 16, further including: adding signals to or dropping signals from the WDM signals. 20. The method of claim 19, wherein dropping the signals from the WDM signals includes filtering signals to be dropped with tunable filters included in or optically coupled to the routing module. 21. The method of claim 19, wherein filtering signals includes filtering a signal associated with a colorless drop port with a tunable filter dedicated to a particular interface of the optical node. 22. A method of routing wavelength division multiplexed (WDM) signals, comprising: transmitting or receiving WDM signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths using at least two reconfigurable optical add/drop multiplexers (ROADMs); anddirecting, by a routing module coupled to at least a subset of the at least two ROADMs, signals to different internode network paths, simultaneously, the directed signals include distinct signals of the same wavelength;wherein directing signals includes (i) routing drop signals to drop ports using a multicast switch and (ii) routing add signals using an aggregate switch to at least one ROADM, of the at least a subset of the at least two ROADMs, the routed drop signals or the routed add signals include at least two distinct signals of the same wavelength. 23. The method of claim 22, wherein routing the drop signals includes filtering the drop signals routed to drop ports. 24. The method of claim 23, wherein routing the drop signals includes amplifying the drop signals routed to drop ports. 25. The method of claim 22, wherein routing the add signals includes amplifying output signals of the aggregator switch. 26. A method of routing wavelength division multiplexed (WDM) signals, comprising: transmitting or receiving WDM signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths using at least two reconfigurable optical add/drop multiplexers (ROADMs); anddirecting, by a routing module coupled to at least a subset of the at least two ROADMs, signals to different internode network paths, simultaneously, the directed signals include distinct signals of the same wavelength;wherein directing the signals, by the routing module, includes directing the signals through a distribution module optically coupling the routing module to the at least a subset of the at least two ROADMs. 27. The method of claim 26, wherein the at least a subset of the at least two ROADMs is coupled to the distribution module via a corresponding plurality of add/drop ports. 28. The method of claim 26, wherein the at least a subset of the at least two ROADMs are coupled to the distribution module via a corresponding plurality of express ports. 29. A method of routing wavelength division multiplexed (WDM) signals, comprising: transmitting or receiving WDM signals, each WDM signal including multiple signals of different wavelengths, onto or from at least two internode network paths using at least two reconfigurable optical add/drop multiplexers (ROADMs); anddirecting, by a routing module coupled to at least a subset of the at least two ROADMs, signals to different internode network paths, simultaneously, the directed signals include distinct signals of the same wavelength;wherein the routing module includes at least one expansion port to couple at least one ROADM, of the at least a subset of the at least two ROADMS, optically to one or more other routing modules and wherein directing signals further includes directing signals from the one or more ROADMs to the one or more other routing modules through the at least one expansion port.