| 摘要 |
<P>PROBLEM TO BE SOLVED: To realize a coherent light transmitting method for transmitting a multivalued signal without being influenced principly by phase fluctuation included in a light source. <P>SOLUTION: A multivalued modulation code string and a reference code string are optically modulated respectively, two optically modulated optical carriers are transmitted through two optical paths, two transmitted optical signals are received, and these optical signals are mixed with two local oscillation beams having correlation with the two optical signals respectively to perform optical heterodyne detection. Then an intermediate frequency signal is selected, electric signals corresponding to the multivalued modulation code string and the reference code string are obtained, the two electric signals are multiplied with each other, a low frequency band signal is selected from the signals obtained by the multiplication to restore the multivalued modulation code, and the multivalued modulation code is further decoded to restore a data string. Alternatively, electric signals are generated by an optical self-homodyne detection and the low frequency component of a difference signal between the two electric signals is selected to restore the multivalued modulation code. <P>COPYRIGHT: (C)2007,JPO&INPIT |
