Path computation engine and method of configuring an optical path for quantum key distribution

1. A path computation engine for an optical communications network, the optical communications network comprising a plurality of nodes and a plurality of links, wherein the path computation engine comprises a processor and memory, the memory comprising instructions executable by the processor whereby the path computation engine is configured to:

receive a request to configure a quantum key (Qkey) path from a first node to a second node in the optical communications network for a quantum key distribution (QKD) signal for a quantum key for a secure data transmission signal;

calculate a feasible Qkey path from the first node to the second node that is logically different to a traffic path from the first node to the second node for the secure data transmission signal, wherein the Qkey path is feasible if an optical signal power originating from the secure data transmission signal within the Qkey path, caused by optical interference of the secure data transmission signal with the QKD signal, is below a predetermined threshold value; and

generate a control signal comprising instructions arranged to configure said feasible Qkey path.

2. The path computation engine of claim 1 , wherein the memory comprises instructions executable by the processor whereby the path computation engine is further configured to calculate at least one of: a raw key bit rate for transmission of a quantum key on the QKD signal depending on transmission characteristics of the calculated feasible Qkey path; and a quantum bit error rate for transmission of a quantum key on the QKD signal depending on transmission characteristics of the calculated feasible Qkey path.

3. The path computation engine of claim 1 , wherein the memory comprises instructions executable by the processor whereby the path computation engine is further configured to:

receive a request to configure a new Qkey path from the first node to the second node for a new quantum key for the secure data transmission signal; and

calculate a new feasible Qkey path from the first node to the second node that is logically different to the traffic path from the first node to the second node and is different to a previous Qkey path from the first node to the second node for a previous quantum key.

4. The path computation engine of claim 1 , wherein the memory comprises instructions executable by the processor whereby the path computation engine is configured to calculate a feasible Qkey path by:

calculating a plurality of feasible Qkey paths from the first node to the second node, each calculated Qkey path being logically different to the traffic path; and

randomly selecting one of said plurality of feasible Qkey paths.

5. The path computation engine of claim 1 , wherein the memory comprises instructions executable by the processor whereby the path computation engine is operative to assign a respective randomly calculated weight value to each link of the optical communications network and to calculate a feasible Qkey path depending on said weight values.

6. The path computation engine of claim 1 , wherein the memory comprises instructions executable by the processor whereby the path computation engine is configured to calculate a feasible Qkey path from the first node to the second node that is physically different to the traffic path from the first node to the second node.

7. The path computation engine of claim 1 , wherein the memory comprises instructions executable by the processor whereby the path computation engine is configured to calculate a feasible Qkey path from the first node to the second node that does not include a repeater.

8. A secure data transmission apparatus for an optical communications network, the secure data transmission apparatus comprising:

a traffic path computation engine comprising a processor and memory comprising instructions executable by the processor whereby the traffic path computation engine is configured to:

receive a request to configure a traffic path from a first node to a second node in the optical communications network for a secure data transmission signal;

calculate a traffic path from the first node to the second node for the secure data transmission signal; and

generate a control signal comprising instructions arranged to configure the calculated traffic path; and

a path computation engine comprising a processor and memory, the memory comprising instructions executable by the processor whereby the path computation engine is configured to:

receive, from the traffic path computation engine, a request to configure a quantum key (Qkey) path from a first node to a second node in the optical communications network for a quantum key distribution (QKD) signal for a quantum key for a secure data transmission signal;

calculate a feasible Qkey path from the first node to the second node that is logically different to a traffic path from the first node to the second node for the secure data transmission signal, wherein the Qkey path is feasible if an optical signal power originating from the secure data transmission signal within the Qkey path, caused by optical interference of the secure data transmission signal with the QKD signal, is below a predetermined threshold value; and

generate a control signal comprising instructions arranged to configure said feasible Qkey path.

9. The secure data transmission apparatus of claim 8 , wherein the apparatus is configured to periodically calculate a new Qkey path for a new quantum key.

10. An optical communications network node comprising a path computation engine comprising a processor and memory, the memory comprising instructions executable by the processor whereby the path computation engine is configured to:

receive a request to configure a quantum key (Qkey) path from a first node to a second node in the optical communications network for a quantum key distribution (QKD) signal for a quantum key for a secure data transmission signal;

calculate a feasible Qkey path from the first node to the second node that is logically different to a traffic path from the first node to the second node for the secure data transmission signal, wherein the Qkey path is feasible if an optical signal power originating from the secure data transmission signal within the Qkey path, caused by optical interference of the secure data transmission signal with the QKD signal, is below a predetermined threshold value; and

generate a control signal comprising instructions arranged to configure said feasible Qkey path.

11. A method of configuring an optical path for quantum key distribution in an optical communications network, the method comprising steps of:

receiving a request to configure a quantum key (Qkey) path from a first node to a second node in the optical communications network for a quantum key distribution (QKD) signal for a quantum key for a secure data transmission signal;

calculating a feasible Qkey path from the first node to the second node that is logically different to a traffic path from the first node to the second node for the secure data transmission signal, wherein the Qkey path is feasible if an optical signal power originating from the secure data transmission signal within the Qkey path, caused by optical interference of the secure data transmission signal with the QKD signal, is below a predetermined threshold value; and

generating a control signal comprising instructions arranged to configure said feasible Qkey path.

12. The method of claim 11 , further comprising calculating at least one of: a raw key bit rate for transmission of a quantum key on the QKD signal depending on transmission characteristics of the calculated feasible Qkey path; and a quantum bit error rate for transmission of a quantum key on the QKD signal depending on transmission characteristics of the calculated feasible Qkey path.

13. The method of claim 11 , further comprising:

receiving a request to configure a new Qkey path from the first node to the second node for a new quantum key for the secure data transmission signal; and

calculating a new feasible Qkey path from the first node to the second node that is logically different to the traffic path from the first node to the second node and is different to a previous Qkey path from the first node to the second node for a previous quantum key.

14. The method of claim 13 , wherein calculating a feasible Qkey path comprises:

calculating a plurality of feasible Qkey paths from the first node to the second node, each calculated Qkey path being logically different to the traffic path; and

randomly selecting one of said plurality of feasible Qkey paths.

15. The method of claim 13 , wherein calculating a feasible Qkey path comprises:

assigning a respective randomly calculated weight value to each link of the optical communications network; and

calculating a feasible Qkey path depending on said weight values.

16. The method of claim 11 , wherein the method comprises calculating a feasible Qkey path from the first node to the second node that is physically different to the traffic path from the first node to the second node.

17. The method of claim 10 , wherein the method comprises calculating a feasible Qkey path from the first node to the second node that does not include a repeater.

18. The method of claim 11 , wherein the method comprises periodically calculating a new Qkey path for a new quantum key.