Abstract: A method of transmitting data signals via an optical fiber between two network elements (14, 36, 43, 56) in a digital data transmission network comprises using a transmission protocol, wherein, in addition to said data signals, first control and/or monitor signals in the form of overhead signals are transmitted. An optical fiber amplifier (23) is inserted in the optical fiber between the two network elements. Additionally, second control and/or monitor signals in a format corresponding to said overhead signals are transferred between the optical fiber amplifier and at least one of the two network elements. An amplifier unit (22, 48) comprising an optical fiber amplifier (23) is adapted to be inserted in an optical fiber for the transmission of data signals between two network elements (14, 36, 43, 56) in such a data transmission network.

Abstract: An optical amplifier comprises an active fiber (1), a pump unit (2) spaced from the active fiber and adapted to give a nominal, continuous pump power in an operational state, and a pump fiber (3) adapted to transfer optical pump power from the pump unit (2) to the active fiber (1). Moreover, in a safety state, the pump unit (2) is adapted to give a pulsed pump power whose mean power is lower than a prescribed safety limit.