This paper reports on the theoretical and experimental investigations concerning the dynamic capabilities of the hybrid fiber-optic voltage and current sensors intended for the monitoring of remotely operated electrical submersible plant utilized within the oil and gas industry. The voltage sensor comprises a multilayer piezoelectric stack acting as a voltage-to-strain transducer and a fiber Bragg grating (FBG) used to measure voltage induced strain changes within the stack In order to measure current; the same sensor type is used to monitor a specially designed ferrite-core current transformer. It is demonstrated, for the first time, that these types of transducers are capable of measuring higher order voltage and current harmonics - the capability that is invaluable for plant diagnostic and control purposes. The respective sensors are excited using 50-Hz voltage and current square-waves to provide a wide range of harmonic content. It is demonstrated that the sensors are capable of measuring up to the 100,h harmonic (5 kHz), limited only by the experimental set-up.