| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical modulator which is low in driving voltage and can perform a modulation at a high speed. SOLUTION: The optical modulator includes: an interaction portion which has a substrate 1, where an optical waveguide 3 is formed, and a traveling wave electrode 4, and in which the phase of light is modulated by the traveling wave electrode 4 by being applied with a high-frequency electric signal; an input feed-through portion in which the high-frequency electric signal is applied from an external circuit through a connector; and an output feedback portion in which the high-frequency electric signal propagated in the interaction portion is output, wherein an envelope of power reflectivity is -10 to -15 dB at one frequency within a frequency range of about 20% to 30% of an operation bit rate. The optical modulator has an impedance conversion portion which has a maximum point where a primary differential of the envelope of the power reflectivity is zero and a secondary differential is positive within a frequency range of about 40% to 70% of the operation bit rate and is at least partially lower than characteristic impedance of the connector or external circuit so that the power reflectivity at the maximum point is≤-15 dB. COPYRIGHT: (C)2009,JPO&INPIT
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