| 摘要 |
<P>PROBLEM TO BE SOLVED: To generate a multilevel quadrature amplitude modulation signal of eight values or more by one parallel type Mach-Zehnder type amplitude modulation circuit. <P>SOLUTION: D/A conversion is performed to a binary data signal, the binary data signal is output as two sets of parallel binary data signals of m system and n system (m, n≥2), analog signals at a 2<SP>m</SP>level and a 2<SP>n</SP>level are generated from the parallel binary data signals of the m system and the n system, respectively, and drive signals of a Mach-Zehnder type amplitude modulation unit which superimposes an in-phase component of amplitude modulation to an optical signal and a Mach-Zehnder type amplitude modulation unit which superimposes a quadrature component of amplitude modulation to the optical signal are electrically limited, to be supplied by allowing the maximum amplitude to be within the range of a Mach-Zehnder linear modulation area. <P>COPYRIGHT: (C)2011,JPO&INPIT |
