A time domain illumination attenuation system for attenuating a light beam's brightness using an optical fiber adapted to receive a light beam from a light source and direct light from the light beam to a surgical site, comprising: an optical fiber; an interrupter positioned and operable to move into and out of a path of the light beam between the light source and the optical fiber to block the light beam when the light beam is fully incident on the interrupter; an actuator coupled to the interrupter adapted to move the interrupter between a position in which the light beam is unhindered by the interrupter and a position in which the light beam is incident on the interrupter; a controller coupled to the actuator and operable to control the actuator to move the interrupter with a repetition rate so that the light beam is unhindered for a first portion of a cycle and the light beam is incident on the interrupter for a second portion of the cycle, wherein the cycle time of the interrupter is the sum of the unhindered and interrupted time for a cycle, the repetition rate is the number of cycles in a given time period, and the duty cycle is the ratio of unhindered time to the cycle time, characterized in that; the interrupter is arranged with its axis perpendicular to the light beam and is adapted to be alternately rotated 90° into and out of the light beam, the actuator is adapted to rotate the interrupter back and forth to move the interrupter into and out of the path of the light beam, and the controller is adapted to permit selection of a particular repetition rate of greater than 30 cycles per second so that if the duty cycle is greater than 0% and less than 100% of the cycle time, the human eye will not perceive flickering of the light. an interrupter positioned and operable to move into and out of a path of the light beam between the light source and the optical fiber to block the light beam when the light beam is fully incident on the interrupter; an actuator coupled to the interrupter adapted to move the interrupter between a position in which the light beam is unhindered by the interrupter and a position in which the light beam is incident on the interrupter; a controller coupled to the actuator and operable to control the actuator to move the interrupter with a repetition rate so that the light beam is unhindered for a first portion of a cycle and the light beam is incident on the interrupter for a second portion of the cycle, wherein the cycle time of the interrupter is the sum of the unhindered and interrupted time for a cycle, the repetition rate is the number of cycles in a given time period, and the duty cycle is the ratio of unhindered time to the cycle time, characterized in that; the interrupter is arranged with its axis perpendicular to the light beam and is adapted to be alternately rotated 90° into and out of the light beam, the actuator is adapted to rotate the interrupter back and forth to move the interrupter into and out of the path of the light beam, and the controller is adapted to permit selection of a particular repetition rate of greater than 30 cycles per second so that if the duty cycle is greater than 0% and less than 100% of the cycle time, the human eye will not perceive flickering of the light.