Patent ID: 7242864

Claim:
A method for maintaining a required value of power per optical channel in a chain of optical nodes connected by optical fiber spans, wherein at least some of said nodes including optical amplifiers with controllable gains, the method comprising: performing automatic gain control at said optical amplifiers so that, in the frame of power gain of an optical amplifier, to compensate a preceding span loss; said span loss being power loss on an optical fiber span incoming said amplifier; obtaining information from a preceding node in the chain about a value of measured output power (MOP) of the preceding node; measuring input power (MIP) at a following node; obtaining a difference between the MOP of the preceding node and the MIP of the following node to calculate the span loss between the two nodes, wherein the automatic gain control is performed at the amplifier of the following node in response to the calculated span loss; and obtaining, from said preceding node, information about power loss (ΔPL) which has not been compensated at the preceding node, thereby ensuring distributed compensation of power loss changes if occur in one or more spans of the chain.