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

Two electrooptic materials, deuterated cesium dihydrogen arsenate (D-CDA, CsD(2)AsO(4)) and lithium tanta-late (LiTaO(3)), 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-Omega 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 LiTaO(3) modulator figure of 1.23. Direct Current contrast ratio measurements for D-CDA and LiTaO(3) were 50:1 and 20:1, respectively.