Taking cues from the evolution of the electronic IC technologies, the future development of opto-electronic integrated circuit's (OEICs) needs CAD models and tools, in addition to developing better and more devices. OEUT- Spice was developed to address some of these needs, and to self-consistently treat the electro-opto-thermal interactions between devices, and to become a design and simulation tool for integrated OE circuits. We report on our lab's development over the past few years of this model and some of the effects of the electro-opto-thermal interactions on the devices' performance in the circuit. The implementation of this model in a Spice-compatible format is performed by introducing lumped elements: equivalent optical and thermal capacitors, resistors, and non-linear dependant sources, with sub-circuit dedicated to a key physical mechanism. The result is a CAD tool for design and optimization of OEICs, named University of Toronto Optoelectronics SPICE, or OEUT-Spice. As intended, it can be easily adopted by a very large user group with an electronic IC design background, who are likely to be the future OEICs system designers. To validate the model and extract structure dependent model parameters, we have conducted a number of experiments on lasers, laser arrays and transistors, as well as drawing from experimental results from the literature, and we have consistently obtained good agreements in L-I, I-V, transient responses and emission wavelengths under various temperatures, materials, biases, duty cycles and inter-device spacings. As examples, detailed accounts of results for laser, laser array, and HBT-laser module are presented.