Method for pre-emphasis of optical signals in a transmission system comprising add-drop-modules

A method for pre-emphasis of an optical wavelength division multiplex signal of which signals with different wavelengths assembled in groups are transmitted over a channel of a transmission link with a number of sections and network elements, the channel selected from the group consisting of express channel, drop channel, add channel, and add-drop channels, the method comprising:

• transmitting from a first network element to a second network element for the express channel;
• injecting drop channels, add channels or add-drop channels at drop points that are arranged between the first and second network elements;
• and
• achieving predetermined average optical signal-to-noise ratios in a network element for a termination group of signals and an injection point of the group, an average and an individual-channel power setting of the signals for the termination group, wherein for a non-termination group of signals the average power is set at a preceding network element, wherein
• depending on a encoding type of a counter and of a marking for dropping a group, a regulation protocol provided at a selected controlling network element for control of pre-emphasis steps with sub-pre-emphasis settings and/or the additional individual-channel pre-emphasis of the groups along the transmission link is selected, and
• after a receipt of a data packet having the counter with a value of 0, a network element controls the pre-emphasis steps for its subsequent network sections and the counter is incremented to 1, and
• at the injection point, the average signal power of a group with drop channels dropped at a subsequent drop point is reduced in favor of the average signal power of an onwards-routed group of express channels, or the average signal power of a group with add-drop channels dropped at a subsequent drop point is reduced in favor of the average signal power of an onwards-routed group of express channels, or the average signal power of a group with drop channels terminated at a subsequent drop point is reduced in favor of the average signal power of an onwards-routed group of express channels, or the average signal power of a group with add-drop channels terminated at a subsequent drop point is reduced in favor of the average signal power of an onwards- routed group of express channels.