| 摘要 |
A multilevel light intensity modulation system can generate a multilevel modulated optical signal from a single light source without handling multilevel electrical signals. The light from a light source 1 is branched by a Y-branch 40 into two light beams, which are phase-modulated by phase modulation sections 41, 42 with two sequences each of a bi-level electrical signal. The phase-modulated light beams are coupled by a directive coupler 43 to generate intensity-modulated output light beam. Phase modulation sections 41, 42 provide a phase difference between the branched light beams approximately of 0, (3/8)pi, (5/8)pi and as depending on level combinations of the two sequences each composed of a bi-level electrical signal. This enables multilevel light modulation in the light domain.
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