| 摘要 |
<P>PROBLEM TO BE SOLVED: To stabilize transmission of a sub-signal superimposed on main signal light, irrespective of the intensity of the main signal light, while using a general-purpose main signal light transmission device. <P>SOLUTION: A sub-signal modulation device comprises a sub-signal output 221 for outputting a different sub-signal from the main signal; an optical variable attenuation unit 222 for carrying out variable attenuation with speed of response later than one half of speed of this main signal about the main signal light by which this main signal is modulated; a setter 223 of attenuation amount for setting up the amount of attenuation given by this variable attenuation unit 222 according to this sub-signal outputted in this sub-signal output 221, so as to make this sub-signal superimpose on this main signal light according to the amount of attenuation given by this variable attenuation unit 222; and a stabilization control unit 224 for controlling the setter 223 of the attenuation amount, so that the amplitude of the amount of attenuation in this variable attenuation unit 222 may be made a fixed ratio stable to the average intensity of this main signal light. <P>COPYRIGHT: (C)2007,JPO&INPIT |
