Patent ID: 6847788

Claim:
A transmission characteristic equalizing system, comprising: at least one optical tunable filter having a variable transmission factor versus wavelength characteristic and placed along an optical transmission path between a transmitting station and a receiving station in a wavelength division multiplexing optical communication system; a transmission characteristic measurement unit measuring transmission characteristics of optical signals of different wavelengths transmitted over the optical transmission path; and a transmission characteristic control unit, based on measurements made by the transmission characteristic measurement unit, controlling amounts of pre-emphasis in the transmitting station and the transmission factor versus wavelength characteristic of the optical tunable filter to thereby equalize the transmission characteristics for the optical signals, wherein the transmission characteristic control unit calculates an optimum allocation between a controlled variable of the amounts of pre-emphasis in the transmitting station and a controlled amount of the transmission factor versus wavelength characteristic of the optical tunable filter and controls the amounts of pre-emphasis and the transmission factor versus wavelength characteristic according to the optimum allocation to thereby equalize and optimize the transmission characteristics, and wherein the transmission characteristic measurement unit measures first and second transmission characteristic values having a correlation with each other as the transmission characteristics, and the transmission characteristic control unit first controls only the transmission factor versus wavelength characteristic of the optical tunable filter to equalize the first transmission characteristic values and then temporarily equalize the second transmission characteristic values with reference to the equalized first transmission characteristic values, then calculates the optimum allocation with reference to the transmission factor versus wavelength characteristic of the optical tunable filter at a time of temporary equalization of the second transmission characteristic values, and controls the transmission factor versus wavelength characteristic of the optical tunable filter and the amounts of pre-emphasis in the transmitting station according to the optimum allocation to thereby equalize the second transmission characteristic values.