Optical devices are provided for optical signal modulation under the control of an electrical signal propagating along a traveling wave electrode structure. The electrode structure comprises a coplanar stripline including a control signal electrode interposed between a pair of ground plane electrodes. Each of the ground plane electrodes defines a positively or negatively biased elevated ground plane portion isolated from the control signal input and the control signal output. The present invention also contemplates provision of a coplanar stripline as described and claimed herein.