Patent ID: 7982865

Claim:
A method for monitoring an optical amplifier having an optical path extending between an optical input port and an optical output port with an optical amplification element located within the optical path, and further having a pumping source which applies an optical pumping power (P pump ) to the optical path via a coupling unit connected within the optical path, the optical input port receiving an optical signal at an optical input signal power (P in ) and the optical output port emitting an optical signal at an optical output signal power (P out ) with a gain (G) controlled to a predetermined nominal value, the method including: (a) determining the functional dependence of the optical pumping power (P pump ) on the optical input signal power (P in ) or the optical output signal power (P out ) for the predetermined nominal value of the gain (G); (b) determining a current optical pumping power value (P pump,1 ) by the functional dependence determined at step (a) and a currently detected optical input signal power value (P in,1 ) or a currently detected optical output signal power value (P out,1 ); (c) determining a currently valid value for a proportionality constant α(t 1 ) with the current optical pumping power value (P pump,1 ) determined at step (b) and a currently detected first electrical pumping current value (I pump,1 ), wherein the proportionality relationship P pump =α(t)·I pump is presumed where P pump is the optical pumping power value, I pump is the electrical pumping current value, and α(t) is a time-variant proportionality constant that is subject to a degradation over time; (d) determining a maximum possible pumping power value (P pump,max ) from a maximum permissible electrical pumping current value (I pump,max ) and from the currently valid value α(t 1 ) by means of the proportionality relationship; and (e) determining a maximum optical input signal power value (P in,max ) from the maximum possible pumping power value (P pump,max ) and from the inverse functional dependence of the optical pumping power on the optical input signal power as determined in step (a), where the optical input signal power is expressed directly or in terms of the ratio of the optical output signal power to the gain (G), or determining the maximum optical output signal power value (P out,max ) from the maximum possible pumping power value (P pump,max ) and from the inverse functional dependence of the optical pumping power on the optical output signal power as determined in step (a), where the optical output signal power is expressed directly or in terms of the product of the optical input signal power and the gain (G).