Signalling in optical transmission networks

A method of operating a node in a connection-oriented optical network in which connections between nodes of the network are carried by optical channels, the node having an optical amplifier and a power control unit for controlling the optical amplifier, the method comprising:

• receiving signalling at the node;
• adjusting the optical amplifier, in response to the signalling, to at least one of:
• support a new optical channel to be used by a new connection;
• and
• switch off an existing optical channel used by an existing connection;
• wherein the signalling instructs the power control unit of the node and a power control unit of a downstream node to adjust their respective optical amplifiers in parallel with each other.

Apparatus configured as a node in a connection-oriented optical network in which connections between nodes of the network are carried by optical channels, the apparatus comprising:

• an optical amplifier;
• a power control unit configured to control the optical amplifier;
• a signalling module configured to receive signalling;
• and
• wherein the power control unit is configured to adjust the optical amplifier, in response to signalling received by the signalling module, to at least one of:
• support a new optical channel to be used by a new connection;
• and
• switch off an existing optical channel used by an existing connection;
• wherein the signalling is configured such that the power control unit of the node and a power control unit of a downstream node adjust their respective optical amplifiers in parallel with each other.

A machine-readable medium comprising instructions for causing a processor to perform a method of operating a first node in a connection-oriented optical network comprising nodes and optical links between nodes, each node having a power control unit for controlling an optical amplifier at the node, the method comprising, at the first node, at least one of:

• in response to a requirement to set up a new connection in the network, signalling to the power control unit at each of a plurality of downstream nodes along a path of the new connection to cause the power control unit to adjust its respective optical amplifier to support a new optical channel to carry the new connection;
• and
• in response to a requirement to tear-down an existing connection in the network, signalling to the power control unit at each of a plurality of downstream nodes along a path of the existing connection to cause the power control unit to adjust its respective optical amplifier to switch off an existing optical channel used by the existing connection;
• wherein the signalling is configured such that the power control units of the downstream nodes adjust their respective optical amplifiers in parallel with each other.