Abstract: For checking the transmission in an optical transmission installation with optical fibers for conducting optical useful signals between signal sources and signal acceptors (S/D), at which optical useful signals are coupled into or outcoupled from the optical fibers, which signals can be diverted to substitute paths at nodes (OCC) of the transmission device, checking signals (LS) are transmitted in both directions between the signal sources and signal acceptors (S/D) and nodes (OCC) as applicable in the respective optical fiber for at least one useful signal. The presence of the checking signals (LS) is checked, and in the absence of a checking signal (LS) from one line direction, the transmission of a checking signal (LS) in the opposite direction is suppressed. In this way it is assured that on both sides of a line problem, this problem will be detected and an alarm will be tripped if necessary, or a switchover will be made to a substitute path.

Abstract: An integrated optical circuit is described for coupling an optical fiber amplifier with two or four terminals in such a way that the optical fiber amplifier is supplied with optical signals in a prescribed direction, and the optical signals are coupled out to an optical network via a directed directional coupler. The necessary optical switches, couplers, terminals and light guides are integrated into the integrated optical circuit.