Abstract: An optical transmission system allows for the remote determination of the total output power of each repeater. The optical transmission system includes two terminals, an optical path that transmits a plurality of optical signals between the two terminals, and a plurality of repeaters spaced along the optical path. In each of the repeaters, pilot signals are inserted by impressing them upon the amplified optical signals output from the repeater. The pilot signals are derived from an oscillator whose frequency is unique to the repeater in which the pilot signals are inserted. The magnitude of each pilot signal is proportional to the output power of its associated repeater. Each terminal provides a measurement of the total power output from each repeater using a receiving device. The receiving device selects the unique oscillator frequency for each of the repeaters desired to be measured, and measures the pilot signals at the selected frequency.