An electric current measurement device includes a housing defining first and second open ends sealed by first and second sealing means, respectively: a first optical fiber received in an aperture in the first sealing means and in optical communication with a first optical lens in the housing; a first polarization filter in the housing in optical communication with the first lens; a magneto-optical rod within the housing in optical communication with the first polarization filter; a second polarization filter in the housing in optical communication with the rod; and a second optical lens in the housing in optical communication with the second polarization filter. The second sealing means has an aperture for receiving a second optical fiber fixed to the second lens. First and second lids, attachable to the first and second housing ends, respectively include apertures for receiving the first and second optical fibers, respectively.