In a method of fabricating a traveling wave optical modulator, an optical
waveguide structure having an optical waveguide and a signal electrode
path extending from a signal input to a termination output is formed. The
signal electrode path is modified to include a customized signal
electrode having a transmission line characteristic substantially
matching a target transmission line parameter value. In another aspect, a
traveling wave optical waveguide structure includes an optical waveguide
and a signal electrode path. The signal electrode path extends from a
signal input to a termination output and is defined by an electrode seed
structure. The electrode seed structure is exposed for subsequent
electrode formation and has a transmission line characteristic
detrimental to proper propagation of an electrical modulation signal.