| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a multi-level intensity modulation system for generating a multi-level modulated optical signal from one light source without handling a multi-level electric signal. <P>SOLUTION: A light beam from a light source 1 is branched into two by a Y branch 40, and branch light beams are phase-modulated by phase modulation sections 41 and 42 respectively according to binary electric signals of two series. The phase-modulated light beams are coupled by a directional coupler 43 to obtain an intensity-modulated output light beam 50. In the phase modulation sections 41 and 42, phase differences are set to about 0, (3/8)π, (5/8)π, and π between the branch light beams at symbol points of the electric signals according to combinations of levels of the binary electric signals A and B of the two series. Consequently, multi-level modulation in an optical area can be performed. <P>COPYRIGHT: (C)2008,JPO&INPIT |
