| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a system and a method each effective and having large cost effectiveness in connection with monitoring modulation. <P>SOLUTION: The system and the method for modulating a supervisory signal on a wavelength division multiplexing (WDM) channel use a variable optical attenuator (VOA) for performing amplitude modulation of the supervisory signal. As another method, at least two spectrum bands of the supervisory signal are subjected to the amplitude modulation by the VOA accompanied with a phase difference though the same frequency (preferably with a reverse phase) in which a signal acquired by synthesis of these two spectrum bands is to be maintained to a predetermined value, to be preferably maintained to the minimum value, and to be further more preferably maintained to a zero value. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
