| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a signal modulation device and a method of the same to obtain an optical signal of high quality and multiple values. <P>SOLUTION: A signal modulation device for modulating an electric two-value signal of N channels (N is an integer no less than 2 and no more than N) into an optical multiple-value signal of a single channel comprises N steps of modulation parts for modulating an electric signal into an optical signal. The modulation part of a first step modulates a first electric two-value signal into an optical signal to supply to a second step modulation part. The modulation parts from the second step on modulate an electric signal into an optical signal by an external modulation system. The modulator of the mth step (m is an integer no less than 2 and no more than N) modulates the mth electric two-value signal into an optical signal and outputs it, and also outputs the optical signal output by the modulation part of the Nth step as an optical multiple-value signal, with the optical signal output from the modulation part of the m-1th step as a light source. <P>COPYRIGHT: (C)2012,JPO&INPIT |
