A system is provided for characterizing optical fibers carrying signal
traffic. The system includes a transmitter, a variable optical attenuator
(VOA), a receiver, and a computing device. The transmitter propagates an
optical test signal along a channel of a fiber pathway. The VOA adjusts
the attenuation of the optical test signal from an initial, greater
attenuation to a subsequent, lesser attenuation. At the same time, the
computing device monitors at least one other channel of the fiber pathway
and identifies effects upon the other channel(s) from the optical test
signal. The computing device may communicate with the VOA and with other
components of the fiber pathway to direct adjustment of the signal
strength. A maximum optical test signal strength may thus be achieved
that does not negatively affect signal traffic on the other channels, and
the fiber pathway may subsequently be tested using the achieved maximum
optical test signal strength.