We have characterized the role of electro-optic field shielding effect in bulk CdTe:In rods at 1550 nm. Different temperatures, modulating frequencies and probe beam power have been tested. Experimental results agree with a dielectric relaxation explanation, when taking into account the high injection regime and the contribution of collection of photo-generated free excess carriers at the contacts. The lowering in electro-optic yield can be minimized by a suitable reduction in operating temperature and sample dimensions, having defined the optical power of the signal to be processed.