Patent ID: 7725033

Claim:
An optical wavelength controlling method performed by an optical wavelength controlling system of an optical wavelength division multiplexing transmission system wherein a plurality of wavelengths of channels which wavelengths are multiplexed and transmitted by an optical transmitting unit, and the multiplexed wavelengths are divided into the wavelengths of the channels by an optical receiving unit, the optical wavelength controlling method comprising: reducing, by an optical power reducing unit of the optical wavelength controlling system, optical power of one of the wavelengths of the channels in the optical transmitting unit, which one is the wavelength of a target channel, and transmitting the wavelengths; evaluating, by a wavelength shift detecting unit of the optical wavelength controlling system, channel crosstalk in the optical receiving unit based on a code error rate of a channel adjacent to the target channel, and detecting a shift of the wavelength of the target channel in the optical transmitting unit; and compensating for the shift of the wavelength of the target channel in the optical transmitting unit, by a wavelength shift compensation unit of the optical wavelength controlling system, based on a result of the evaluation of the channel crosstalk.