Optical transmission equipment for suppressing a four wave mixing and optical transmission system

An optical transmission system, comprising:

• a first optical transmission apparatus which amplifies a wavelength-division-multiplexed signal and sends it to an optical fiber;
• and
• a second optical transmission apparatus which receives the wavelength-division-multiplexed signal via the optical fiber, wherein:
• the second optical transmission apparatus comprises:
• means which observe FWM crosstalk of wavelength-division-multiplexed light received from the optical fiber;
• and
• means which send the observed FWM crosstalk to another supervisory and control equipment, wherein:
• the first optical transmission apparatus comprises:
• an optical amplifier which amplifies the wavelength-division-multiplexed light;
• an excitation light source which controls intensity of the wavelength-division-multiplexed light from the optical amplifier;
• a multiplexing section which inputs the excitation light from the excitation light source into the optical amplifier;
• and
• means which output the wavelenght-division-multiplexed light amplified by the optical amplifier to the optical fiber,
• the optical transmission apparatus receiving the FWM crosstalk observed by the second optical transmission apparatus via the supervisory and control equipment and controlling an amount of the excitation light output from the excitation light source acting on the optical amplifier so that the value of the FWM crosstalk becomes a predetermined target value or below.

A transmission method which sends and receives a wavelength-division-multiplexed signal between transmission apparatuses which are connected through an optical fiber, comprising:

• a step to observe FWM crosstalk of wavelength-division-multiplexed light by a receiver transmission apparatus;
• a step to send the observed FWM crosstalk to a sender transmission apparatus;
• and
• a step to adjust intensity of wavelenght-division-multiplexed light output from an optical amplifier to the optical fiber so that the FWM crosstalk becomes to have a predetermined target value or below in the sender transmission apparatus.

A transmission method which sends and receives a wavelength-division-multiplexed signal between transmission apparatuses which are connected through an optical fiber, comprising:

• a step to observe FWM crosstalk of wavelength-division-multiplexed light by a receiver transmission apparatus;
• a step to send the observed FWM crosstalk to a sender transmission apparatus;
• a step to compare the RWM crosstalk and a predetermined threshold value in the sender transmission apparatus;
• a step to adjust intensity of wavelenght-division-multiplexed light output from an optical amplifier to the optical fiber so that the FWM crosstalk becomes to have a predetermined first target value or below when compared result indicates that the FWM crosstalk has the threshold value or higher;
• and
• a step to adjust so that intensity of the wavelength-division-multiplexed light output from the optical amplifier to the optical fiber becomes to have a predetermined target value when the compared result indicates that the FWM crosstalk is smaller than the threshold value.