A system and a method for determining local electric field strengths, the system including: a light source module configured to emit light; a plurality of electric field sensors, each sensor including a light input portion and a light output portion, each sensor including an electro-optic material arranged in a path of at least some of the received light, an optical property of the electro-optic material being variable depending on a local electric field strength at the sensor, and the electro-optic material being arranged in the sensor such that a property of the output light varies depending on the local electric field strength; a light detection module arranged to receive the output light from the sensors; and a processing module in communication with the light detection module, the processing module being programmed to determine a corresponding value for the electric field strength local to each of the sensors.