Patent ID: 6999680

Claim:
A WDM transmission system comprising: a plurality of WDM optical networks, each of said WDM optical network including an optical signal receiver, and an optical signal transmitter, communicably connected to said optical signal receiver, for transmitting, to said optical signal receiver, a WDM signal having a plurality of optical signals at respective different wavelengths with adjusting each of intensities of said plural optical signals by performing preemphasis; and a central controller, communicably connected to said plural WDM optical networks via a plurality of monitor/control lines respectively, including: variation factor monitoring means for monitoring one or more variation factors which requires a new setting for said preemphasis performed by said optical signal transmitter of each said WDM optical network via a respective one of the plural monitor/control lines; and preemphasis controlling means for controlling controlling a status of said preemphasis by adjusting said setting for said preemphasis performed by said optical signal transmitter of each said WDM optical network via the respective monitor/control line based on the result of the monitoring carried out by said variation factor monitoring means, wherein said central controller further includes storing means for storing intensity information of intensities of the optical signals at the respective different wavelengths, which optical signals are included in the WDM signal output from said optical signal transmitter of each said WDM optical network when an initialization for amounts of said preemphasis is performed, and time information of the time when said initialization is performed; said variation factor monitoring means includes elapsed-time monitoring means for monitoring, as one of said variation factors, whether or not a predetermined time period has passed since an initialization of a first optical signal transmitter, which is the optical signal transmitter of one of said plural WDM optical networks based on said time information stored in said storing means; and said preemphasis controlling means includes intensity controlling means for controlling, if the result of said monitoring by said elapsed-time monitoring means is positive, intensities of optical signals in a WDM signal that is to be output from said first optical signal transmitter by adjusting amounts of said preemphasis performed by said first optical signal transmitter in such a manner that said last-named intensities of said first optical signal transmitter become identical with those when said initialization is performed, based on said intensity information stored in said storing means.