Traveling wave amplitude modulator with 1-GHz bandwidth for coherent light optical communication

Abstract
Two elettrooptic materials, deuterated cesium dihydrogen arsenate (D-CDA, CsD2AsO4) and lithium tantalate (LiTaO3), are examined for the application of a traveling wave-type coherent light modulator. The main design goals are (a) low drive power of 4 W for 10% linear amplitude modulation; (b) ±3-dB bandwidth of 1 GHz; and (c) 50-Ω impedance. Experimental performance based on theoretical expectations are presented for both materials. Using a microwave network analyzer, the results indicate that the D-CDA modulator gives better performance with a VSWR of 1.06 as compared with the LiTaO3 modulator figure of 1.23. Direct Current contrast ratio measurements for D-CDA and LiTaO3 were 50:1 and 20:1, respectively.

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