Method of controlling optical signal power at an add/drop node in a WDM optical communication system

A method for controlling signal power of a wavelength division multiplexes (WDM) signal at a network element in a WDM system, the network element adapted for receiving a WDM input signal having a plurality of optical channels, the network element including a first transmission path for adding selected optical channels to the WDM input signal, a second transmission path for routing selected optical channels through the network element that are not being dropped, and a third transmission path for expressly routing selected optical channels of a WDM input signal directly through the network element, the method comprising:

• determining a target power level of the optical channels in the second transmission path;
• adjusting total signal power of the optical channels in the third transmission path to a level that is approximately equal to the target power level of the optical channels in the second transmission path before adjusting signal power of individual optical channels in the first and second transmission paths;
• and
• adjusting signal power of individual optical channels in the first and second transmission paths to approximately correspond with a power divergence profile of optical channels in the third transmission path, wherein the power divergence profile is representative of gain ripple in the WDM input signal.

A method for controlling signal power of a wavelength division multiplexed (WDM) signal at a network element in a WDM system, the network element adapted for receiving a WDM input signal having a plurality of optical channels, the network element including a first transmission path for adding selected optical channels to the WDM input signal, a second transmission path for routing selected optical channels through the network element that are not being dropped, and a third transmission path for expressly routing selected optical channels of a WDM input signal directly through the network element, the method comprising:

• determining a first target signal power for an individual optical channel in the first transmission path such that the first target signal power is at a level that fits into the power divergence profile of the optical channels in the third transmission path;
• determining a second target signal power for an individual optical channel in the second transmission path such that the second target signal power is at a level that fits into the power divergence profile of the optical channels in the third transmission path;
• and
• adjusting signal power of individual optical channels in the first and second transmission paths to approximately correspond with a power divergence profile of optical channels in the third transmission path, wherein the power divergence profile is representative of gain ripple in the WDM input signal.

A method for controlling signal power of a wavelength division multiplexed (WDM) signal at an add/drop node in a WDM system, the add/drop node adapted for receiving a WDM input signal having a plurality of optical channels, the add/drop node including an express transmission path for expressly routing selected optical channels of a WDM input signal directly through the node, a through transmission path for routing selected optical channels through the add/drop node that are not being dropped, and an add transmission path for adding selected optical channels, the method comprising:

• determining a target power level of optical channels in the through transmission path;
• adjusting total signal power of optical channels in the express transmission path to a level that is approximately equal to the target power level of the optical channels in the through transmission path;
• adjusting signal power of individual optical channels in the through transmission path to approximately correspond with a power divergence profile of the optical channels in the express transmission path, wherein the power divergence profile is representative of gain ripple in the WDM input signal;
• and
• adjusting signal power of individual optical channels in the add transmission path to approximately correspond with the power divergence profile of the optical channels in the express transmission path.