| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide quadrature amplitude modulation (QAM) of optical carriers which encodes five or more signal points onto the optical carrier for each encoding interval in relation to modulation of the optical carriers. <P>SOLUTION: The quadrature amplitude modulation of the optical carriers is equipped with an optical splitter, an optical coupler, first and second optical paths, and a digital signal generator. The optical splitter has an input port and first and second output ports. The optical coupler has first and second input ports and an output port. The first optical path couples the first output port of the splitter to the first input port of the coupler. The second optical path couples the second output port of the splitter to the second input port of the coupler. Each optical path includes an electro-optical phase shifter, and one of the optical paths includes an electro-optical attenuator. The digital signal generator is configured to apply binary-valued voltage signals to control inputs of the phase shifter and the attenuator. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
