We present a simulation environment for parallel optoelectronic data-processing systems, and we especially consider the fusion of optoelectronic integrated circuits and optical interconnection modules. hadlop, which stands for hardware description language for optical processing, is a simulator that works at the digital design level. So far, hadlop has allowed algorithm and architecture studies for smart-pixel systems. We have just begun to extend the capabilities of hadlop toward an automatic synthesis tool for three-dimensional optoelectronic VLSI circuits. A hadlop architecture will then be the basis for the automatic generation of detailed construction plans that consider the interaction between optical interconnection modules and optoelectronic integrated circuits. The simulation system is freeware and is available through the Internet at http://www2.informatik.uni-jena.de/pope/HADLOP/hadlop.html.