Optical communication system with a hierarchical branch configuration

1. An optical communication system comprising:

first and second cable landing stations coupled to a trunk path in an optical cable;

at least one hub-node, each of the hub-nodes being coupled to the trunk path through an associated hub-node branching unit;

at least one mid-node, each of the mid-nodes being coupled to at least one of the hub-nodes through an associated mid-node branching unit and an associated mid-node path in the optical cable, the mid-node path not including the trunk path whereby mid-node signals may be communicated between each of the mid-nodes and the at least one of the hub-nodes coupled thereto without being provided on the trunk path; and

at least one sub-node, each of the sub-nodes being coupled to at least one of the mid-nodes through an associated sub-node branching unit and an associated sub-node path in the optical cable, the sub-node path not including the trunk or mid-node path, whereby sub-node signals may be communicated between each of the sub-nodes and the at least one of the mid-nodes coupled thereto without being provided on the trunk or mid-node path.

2. The optical communication system of claim 1 , wherein each of the sub-nodes is coupled to first and second ones of the mid-nodes through the associated sub-node branching unit, and first and second sub-nodes of the associated sub-node path, and wherein the sub-node branching units directly connect optical fibers to provide the associated sub-node path.

3. The optical communication system of claim 1 , wherein each of the sub-nodes is coupled to first and second ones of the mid-nodes through the associated sub-node branching unit and first and second sub-nodes of the associated sub-node paths, and wherein the sub-node branching units comprise an optical add-drop multiplexer to provide the associated sub-node paths.

4. The optical communication system of claim 1 , wherein each of the mid-nodes is configured to send and receive aggregate signals on the mid-node path at a first data rate, and to send and receive sub-node signals to and from ones of the sub-nodes coupled thereto at a second data rate lower than the first data rate.

5. The optical communication system of claim 1 , wherein each of the mid-nodes is configured to send and receive aggregate signals to and from the mid-node path on a different associated wavelength.

6. The optical communication system of claim 1 , wherein at least one of the associated mid-node branching units directly connects optical fibers to provide the associated mid-node path.

7. The optical communication system of claim 1 , wherein at least one of the associated mid-node branching units comprises an optical add-drop multiplexer.

8. The optical communication system of claim 1 , wherein at least one of the hub-nodes comprises a hub-node transponder configured for sending and receiving aggregate signals to and from the trunk path, and a mid-node transponder configured for sending and receiving mid-node signals to and from the associated mid-node path.

9. The optical communication system of claim 1 , wherein at least one of the mid-nodes comprises a mid-node transponder configured for sending and receiving aggregate signals to and from the mid-node path, and a sub-node transponder configured for sending and receiving sub-node signals to and from the associated sub-node path.

10. A optical communication system comprising:

first and second cable landing stations coupled to a trunk path in an optical cable;

a hub-node coupled to the trunk path through an associated hub-node branching unit for receiving first associated aggregate signals from at least one of the first and second cable landing stations, the first associated aggregate signals comprising associated mid-node data, the hub-node being configured to provide mid-node signals;

a plurality of mid-nodes, each of the mid-nodes being coupled to the hub-node through an associated mid-node branching unit and a mid-node path in the optical cable, whereby each of the mid-nodes is configured for receiving an associated one of the mid-node signals through the mid-node path without the associated ones of the mid-node signals being provided on the trunk path, and at least one of the mid-nodes being configured to provide sub-node signals; and

a plurality of sub-nodes, each of the sub-nodes being coupled to at least one mid-node through an associated sub-node branching unit and a sub-node path in the optical cable, whereby each of the sub-nodes is configured for receiving an associated one of the sub-node signals through the sub-node path without the associated ones of the sub-node signals being provided on the trunk or mid-node path.

11. The optical communication system of claim 10 , the system further comprising:

a second hub-node coupled to the trunk path through a second associated hub-node branching unit for receiving second associated aggregate signals from at least one of the first and second cable landing stations, the second associated aggregate signals comprising second associated mid-node data, the second hub-node being configured to provide second mid-node signals,

wherein a plurality of mid-nodes are coupled to the second hub-node through the associated mid-node branching units and a second mid-node path in the optical cable, whereby each of the mid-nodes is configured for receiving an associated one of the second mid-node signals through the second mid-node path without the associated ones of the second mid-node signals being provided on the trunk path.

12. The optical communication system of claim 11 , wherein the first and second hub-nodes are configured to receive the first aggregate signals and the second aggregate signals, respectively, on different associated wavelengths.

13. The optical communication system of claim 10 , wherein the hub-node is configured to receive the first aggregate signals at a first data rate and to send associated ones of the mid-node signals on the mid-node path at a second data rate lower than the first data rate.

14. The optical communication system of claim 10 , wherein at least one of the mid-node branching units directly connects optical fibers to provide the associated mid-node path.

15. The optical communication system of claim 10 , wherein at least one of the associated mid-node branching units comprises an optical add-drop multiplexer.

16. The optical communication system of claim 10 , wherein the mid-node comprises a mid-node transponder configured for sending and receiving aggregate signals to and from the mid-node path, and a sub-node transponder configured for sending and receiving the sub-node signals to and from the sub-node path.

17. The optical communication system of claim 10 , wherein the hub-node comprises a hub-node transponder configured for sending and receiving aggregate signals to and from the trunk path, and a mid-node transponder configured for sending and receiving the mid-node signals to and from the mid-node path.

18. A method of configuring an optical communication system:

coupling a hub-node to a trunk path in an optical cable, the hub-node being configured for receiving first associated aggregate signals transmitted on the trunk path;

coupling a plurality of mid-nodes to the hub-node, each of the mid-nodes being coupled for receiving associated mid-node signals from the hub-node through an associated mid-node path in the optical cable without the associated mid-node signals being provided on the trunk path; and

coupling a plurality of sub-nodes to at least one of the mid-nodes, each of the sub-nodes being coupled for receiving associated sub-node signals from respective mid-nodes through an associated sub-node path in the optical cable without the associated sub-node signals being provided on the trunk path or the mid-node path.

19. The method of claim 18 further comprising:

coupling a second hub-node to the trunk path, the second hub-node being configured for receiving second associated aggregate signals transmitted on the trunk path,

each of the plurality of mid-nodes being coupled for receiving associated second mid-node signals from the second hub-node through a second associated mid-node path in the optical cable without the associated second mid-node signals being provided on the trunk path.

20. The method of claim 18 , wherein the first and second hub-nodes are configured to receive the first aggregate signals and the second aggregate signals, respectively, on different associated wavelengths.