We present a new method for investigation of sensitivity of the integrated optical electrodeless electric field sensor. This method is based on a compact microwave asymmetrical double-ridged waveguide with regular inhomogeneities. Small dimensions of the waveguide along with medium power of the microwave generator produce a strong electric field. The efficiency of the presented experimental unit was verified in the course of testing of the real integrated optical electrodeless electric field sensor (E-sensor).