This study presents an examination of the temperature influence of an EO-modulation system on the basis of its thermo-optic (TO) behavior. We have considered the first order contribution of the temperature to the EO modulator response with emphasis on the direct influence of temperature on the birefringence and on the dimensions of the active part existing between both electrodes. The role of the transverse configuration is examined in comparison with its corresponding longitudinal configuration. Finally, we illustrate this work using some significant results obtained with a lithium tantalate modulator crystal, which is considered as a promising material for EO modulation applications.