Patent ID: 7509055
Filing Date: 2009-03-24
Classification: H04B

Abstract:
1. An optical transmission system for transporting optical signals, comprising: (a) a first optical transmission device that measures an output power level of supervisory control channel signals being transmitted and sends out a downstream message containing the measured output power level; and (b) a second optical transmission device disposed downstream with respect to the first optical transmission device, comprising: an optical transmission unit comprising an optical amplifier unit to boost optical signals and a variable optical attenuator to attenuate the optical signals, and a controller that receives the measured output power level from the first optical transmission device, monitors an input power level of the supervisory control channel signals at the input of the optical amplifier unit, estimates section loss of main optical signals between the first and second optical transmission devices based on the received output power level and the monitored input power level, determines a required attenuation of the variable optical attenuator from the estimated section loss, adjusts the variable optical attenuator accordingly, and selects and sets operating mode of the optical amplifier unit; wherein the controller activates the optical amplifier unit in AGC mode with a gain calculated from the estimated section loss, and sets the optical amplifier unit to operate in ALC mode with an appropriate output power level according to the number of incoming wavelengths, when the supervisory control channel signals indicating transmission of main signals are received.