As the demand for analog-to-digital (A/D) conversion with greater bandwidths increase, it is necessary to look at other alternatives to electronics for integrated circuit design. One such approach to utilize is a combination of optics and electronics, or opto-electronics, at all levels of the system hierarchy. A device that has these properties is the Self Electro-optic Effect Device (SEED), and combining this with oversampling techniques for data conversion can meet the demands for direct digitization of radio frequency (RF) signals. One form of A/D oversampling conversion method is Sigma-Delta modulation. A key element of this technique is the subtractor and in this paper we will discuss the implementation of a differential subtractor using SEEDs as part of a Sigma-Delta Modulator. This paper will detail simulation results based on experimental data to predict the behavior of two types of differential subtractors, one of which will be compared with experimental results.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.