A circuit breaker comprising a hollow insulating column, and an insulated cut-off chamber supported by the column and having movable and fixed contact members therein that are connected to terminals. An optical link current transformer is also provided and comprises a polarized light beam transmitter arranged at the bottom of the column which transmits a beam to the interior of the column, an optical Faraday element, and a toroidal winding directly securing one of the terminals connected to the contact members. The Faraday element is connected to the toroidal winding so as to be subjected to magnetic fields generated by current in the winding. Reflecting mirrors are provided in the column and in the cut-off chamber for transmitting light beams from the transmitter through the column and cut-off chamber and to the Faraday element. Additional reflecting mirrors are provided to transmit light beams from the Faraday element back through the cut-off chamber, the column and then to a photoelectric cell arranged at the base of the column.