| 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, 3-bit input parallel binary data is converted into ternary drive signals of two systems which are constituted of three levels, i.e., 1, 0, -1 and are not simultaneously at the level of 0, and respectively supplied as 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, by allowing the levels of 1, -1 to be two points where the transmittance is the maximum and the phases are mutually inverted only by π radians in the Mach-Zehnder type amplitude modulation unit, and also allowing the transmittance to be the minimum at the level of 0. <P>COPYRIGHT: (C)2011,JPO&INPIT |
