Optical subchannel routing, protection switching and security

Abstract

The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate subcarrier frequencies representing subchannels of an ITU channel to which client signals can be mapped. Client circuits can be divided and combined before being mapped, independent of one another, to individual subchannels within and across ITU channels. Subchannels may be independently routed to a single subchannel receiver filter, such that each subchannel detected at the receiver may come from a different source location. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of client circuits mapped to these subchannels across the nodes of a WDM network. Subchannel hopping may also be used to increase the optical network security.

1 . A system that can route client signals among a plurality of nodes interconnected by one or more fiber optic cables to form an optical network, the system comprising:
 (a) a subchannel mapper that can map each of a plurality of client signals to any available subchannel of any ITU channel, wherein each ITU channel has a predefined ITU frequency and a corresponding plurality of subchannels, and wherein each subchannel has an associated frequency with a predetermined offset from the predefined ITU frequency of the subchannel's corresponding ITU channel;   (b) a first network route that designates the origin of a first client signal at a first node, and a destination for the first client signal at a second node; and   (c) a tunable laser at the first node that can be set to a first subchannel frequency for which the second node has a filter to receive signals transmitted at that subchannel frequency,   (d) whereby the system can route the client signal from the first node to the second node by tuning the laser to the first subchannel frequency and mapping the client signal to the subchannel associated with that subchannel frequency.   
     
     
         2 . The system of  claim 1 , further comprising a fixed add/drop filter that can add or receive client signals transmitted at a predetermined subchannel frequency. 
     
     
         3 . The system of  claim 1 , further comprising a reconfigurable add/drop filter that can be remotely reconfigured to add or receive client signals transmitted at one of a plurality of remotely specified subchannel frequencies. 
     
     
         4 . The system of  claim 1 , further comprising a hardware optical crossconnect switch that can assign each of a plurality of client signals to any of a plurality of available subchannel frequencies, thereby effectively routing any client signal to an available port of any or all nodes of the optical network. 
     
     
         5 . The system of  claim 1 , further comprising software that can remotely set the tunable laser to a second subchannel frequency and add a second network route, thereby effectively controlling the direction in which a second client signal is transmitted on the optical network, as well as the destination nodes that will receive that second client signal. 
     
     
         6 . The system of  claim 1 , wherein subchannel hopping is employed as a security measure to modify over time the subchannel, and associated subchannel frequency, to which a second client signal is mapped. 
     
     
         7 . The system of  claim 1 , wherein the destination for the first client signal is embedded in the in-band overhead channel of the signal containing as its payload the first client signal, thereby enabling the first client signal to be routed by monitoring the overhead channel. 
     
     
         8 . The system of  claim 7 , wherein the destination is embedded in the overhead channel in the form of one of the following:
 (i) an ethernet address; (ii) an IP address; (iii) an MPLS tag; (iv) a VLAN ID; or (v) a TCP port.   
     
     
         9 . A method for routing client signals among a plurality of nodes interconnected by one or more fiber optic cables to form an optical network, the method comprising the following steps:
 (a) mapping each of a plurality of client signals to any available subchannel of any ITU channel, wherein each ITU channel has a predefined ITU frequency and a corresponding plurality of subchannels, and wherein each subchannel has an associated frequency with a predetermined offset from the predefined ITU frequency of the subchannel's corresponding ITU channel;   (b) designating the origin of a first client signal at a first node, and a destination for the first client signal at a second node; and   (c) setting a tunable laser at the first node to a first subchannel frequency for which the second node has a filter to receive signals transmitted at that subchannel frequency,   (d) whereby the client signal can be routed from the first node to the second node by tuning the laser to the first subchannel frequency and mapping the client signal to the subchannel associated with that subchannel frequency.   
     
     
         10 . The method of  claim 9 , further comprising the step of adding or receiving client signals, at a predetermined subchannel frequency, via a fixed add/drop filter. 
     
     
         11 . The method of  claim 9 , further comprising the step of remotely reconfiguring a reconfigurable add/drop filter to add or receive client signals transmitted at one of a plurality of remotely specified subchannel frequencies. 
     
     
         12 . The method of  claim 9 , further comprising the step of assigning, via a hardware optical crossconnect switch, each of a plurality of client signals to any of a plurality of available subchannel frequencies, thereby effectively routing any client signal to an available port of any or all nodes of the optical network. 
     
     
         13 . The method of  claim 9 , further comprising the step of remotely setting the tunable laser to a second subchannel frequency to control the direction in which a second client signal is transmitted on the optical network, and determine the destination nodes that will receive that second client signal. 
     
     
         14 . The method of  claim 9 , further comprising the step of modifying over time the subchannel, and associated subchannel frequency, to which a second client signal is mapped, thereby employing subchannel hopping as a security measure. 
     
     
         15 . The method of  claim 9 , further comprising the step of embedding the destination for the first client signal in the in-band overhead channel of the signal containing as its payload the first client signal, thereby enabling the first client signal to be routed by monitoring the overhead channel. 
     
     
         16 . The method of  claim 15 , wherein the destination is embedded in the overhead channel in the form of one of the following:
 (i) an ethernet address; (ii) an IP address; (iii) an MPLS tag; (iv) a VLAN ID; or (v) a TCP port.   
     
     
         17 . A method for protecting client signals routed along redundant paths among a plurality of nodes interconnected by one or more fiber optic cables to form an optical network, the method comprising the following steps:
 (a) mapping each of a plurality of client signals to any available subchannel of any ITU channel, wherein each ITU channel has a predefined ITU frequency and a corresponding plurality of subchannels, and wherein each subchannel has an associated frequency with a predetermined offset from the predefined ITU frequency of the subchannel's corresponding ITU channel;   (b) defining a working network route that designates the origin of a first client signal at a first node, a destination for the first client signal at a second node, and a working path from the first node to the second node;   (c) defining a protected network route that designates the origin of the first client signal at the first node, a destination for the first client signal at the second node, and a protected path from the first node to the second node;   (d) transmitting the first client signal to the second node along both the working path and the protected path, wherein the first client signal is mapped to both a first subchannel of any ITU channel for transmission along the working path, and a second subchannel of any ITU channel for transmission along the protected path; and   (e) determining whether the second node will receive the first client signal via the working path or the protected path, wherein the the working path is selected by default, except in the event of a failure along the working path, in which case the the protected path is selected until the failure has been repaired.   
     
     
         18 . The method of  claim 17 , wherein each of a plurality of working paths has a corresponding dedicated protected path. 
     
     
         19 . The method of  claim 17 , wherein the protected path can be shared among a plurality of working paths, each assigned to a different subchannel.