A silicon-based optical modulator for transmitting a unary-encoded digital data signal, the modulator comprising: an input waveguiding section for receiving a continuous wave optical input signal; an input optical splitter, coupled to the output of the input waveguiding section for dividing the CW optical input signal into a pair of CW optical input signals; a pair of optical waveguides coupled to the outputs of the input optical splitter and forming a pair of modulator arms; a first plurality of N modulating sections disposed along a first modulator arm of the pair of modulator arms; a second plurality ofN modulating sections disposed along a second, remaining modulator arm of the pair of modulator arms; characterised by: a plurality of drivers, coupled to the first and second pluralities of N modulating sections (50,52), said plurality of drivers configured to be responsive to input signals representing a unary-encoded data signal for turning "on" and "off various ones of the separate modulating sections (50,52) as required to contribute a desired phase shift to the propagating optical signal; an output optical combiner for combining the pair of phase-shifted propagating optical signals into a unary-encoded modulated optical output signal; and an output waveguiding section coupled to the output optical combiner for supporting the propagation of the unary-encoded modulated optical output signal, wherein the modulator further comprises an auxiliary modulating section and associated driver, the auxiliary modulating section isolated from the optical signal path and the associated driver activated to turn "on" the auxiliary modulating section in cases where an odd number of drivers are turned "on", the presence of the auxiliary modulating section creating a return path for current flow and reducing imbalance related thereto within the optical modulator. an input waveguiding section for receiving a continuous wave optical input signal; an input optical splitter, coupled to the output of the input waveguiding section for dividing the CW optical input signal into a pair of CW optical input signals; a pair of optical waveguides coupled to the outputs of the input optical splitter and forming a pair of modulator arms; a first plurality of N modulating sections disposed along a first modulator arm of the pair of modulator arms; a second plurality ofN modulating sections disposed along a second, remaining modulator arm of the pair of modulator arms; characterised by: a plurality of drivers, coupled to the first and second pluralities of N modulating sections (50,52), said plurality of drivers configured to be responsive to input signals representing a unary-encoded data signal for turning "on" and "off various ones of the separate modulating sections (50,52) as required to contribute a desired phase shift to the propagating optical signal; an output optical combiner for combining the pair of phase-shifted propagating optical signals into a unary-encoded modulated optical output signal; and an output waveguiding section coupled to the output optical combiner for supporting the propagation of the unary-encoded modulated optical output signal, wherein the modulator further comprises an auxiliary modulating section and associated driver, the auxiliary modulating section isolated from the optical signal path and the associated driver activated to turn "on" the auxiliary modulating section in cases where an odd number of drivers are turned "on", the presence of the auxiliary modulating section creating a return path for current flow and reducing imbalance related thereto within the optical modulator. a plurality of drivers, coupled to the first and second pluralities of N modulating sections (50,52), said plurality of drivers configured to be responsive to input signals representing a unary-encoded data signal for turning "on" and "off various ones of the separate modulating sections (50,52) as required to contribute a desired phase shift to the propagating optical signal; an output optical combiner for combining the pair of phase-shifted propagating optical signals into a unary-encoded modulated optical output signal; and an output waveguiding section coupled to the output optical combiner for supporting the propagation of the unary-encoded modulated optical output signal, wherein the modulator further comprises an auxiliary modulating section and associated driver, the auxiliary modulating section isolated from the optical signal path and the associated driver activated to turn "on" the auxiliary modulating section in cases where an odd number of drivers are turned "on", the presence of the auxiliary modulating section creating a return path for current flow and reducing imbalance related thereto within the optical modulator.