A signal acquisition probing system uses an optical cavity to acquire a signal under test. The probing system has an optical transmitter and receiver that are coupled to the optical cavity via an optical transmission system. The optical cavity has an electrode structure having apertures formed in the optical cavity that are parallel to propagation path of the optical signal within the cavity. A modulated optical signal is generated by the optical cavity in response to the signal under test creating an electro-magnetic field distribution in electro-optic material in the optical cavity that overlaps the optical path of the optical signal propagating in the optical cavity which varies the index of refraction of electro-optic material in the optical path. The signal acquisition probing system is connected to a measurement instrument to form a voltage measurement system.