For our KDP crystal orientation, various thermo-optic (TO) and relevant temperature-dependence parameters are defined, presented, and studied in the framework of a transverse and a longitudinal electro-optic (EO) modulation systems. This study is based on the concept of the so-called opto-electrical bias ([EQUATION] applied to the system. For both of the above EO-modulation systems, a set of original equations is extracted and investigated with regard to each of the more important TO or temperat