Patent ID: 7668459

Claim:
A method of monitoring a dispersion on a transmission optical fiber in a wavelength division multiplexing optical transmission system in which a transmission distance is fixed and the dispersion of the transmission optical fiber has a slope that changes with respect to temperature changes, said method comprising the steps of: extracting two or more of wavelength channels 1 to n from the transmission optical fiber; and monitoring dispersions of the extracted wavelength channels, comprising the steps of: measuring a first dispersion value in the extracted wavelength channels 1 to n (wavelength: λ mon1 to λ monn ) at a certain temperature T 1 (° C.) measuring a second dispersion value in the wavelength channels 1 to n at a certain other temperature T 2 (° C.); providing dispersion variation amounts ΔD mon1 to ΔD monn in the extracted wavelength channels 1 to n from a difference between the measured first dispersion value and the measured second dispersion value; and providing a dispersion variation amount at an arbitrary wavelength (λ) based on the provided dispersion variation amounts ΔD mon1 to ΔD monn ; wherein the steps of extracting and monitoring are performed by a dispersion monitoring apparatus.