Patent ID: 7031618
Filing Date: 2006-04-18
Classification: H04B

Abstract:
1. An optical transmission system comprising: an optical terminal; an optical-fiber transmission line connected to the optical terminal; and an optical repeater arranged along the optical-fiber transmission line; the optical terminal includes, an optical-signal power detection unit which detects power of optical signals transmitted from the optical terminal in each of a plurality of gain bands, a tone-signal generation unit which generates a plurality of tone signals respectively corresponding to the plurality of gain bands, where each of the plurality of tone signals has a different frequency and a characteristic corresponding to the power of optical signals in one of the plurality of gain bands corresponding to the each of the plurality of tone signals, and an optical transmission unit which transmits the plurality of tone signals together with optical signals through the optical-fiber transmission line, the optical repeater includes, an optical amplification unit which realizes optical amplification in each of the plurality of gain bands with a gain which is determined based on a control signal, a characteristic-signal generation unit which receives the plurality of tone signals, and generates a plurality of characteristic signals each representing the characteristic of one of the plurality of tone signals, and a gain control unit which compares each of the plurality of characteristic signals with a reference signal, and generates the control signal corresponding to each of the plurality of gain bands so as to equalize the gain in the optical amplification in each of the plurality of gain bands, and wherein the characteristic-signal generation unit includes, a photoelectric conversion unit which receives the plurality of tone signals, and generates an electric signal representing the plurality of tone signals, a plurality of frequency filters which respectively extract the plurality of tone signals from the electric signal, and a smoothing unit which smoothes the plurality of tone signals extracted by the plurality of frequency filters so as to generate the plurality of characteristic signals.