Fiber Optic Sensor for Waveguide Arc Detection

Physical Optics Corporation proposes an all optical means for detecting and locating the position of arcing in high power microwave waveguides. When a high-power waveguide is installed in a corrosive environment, joints in the waveguide often deteriorate and gaps develop that lead to arcing and to dangerously high voltage standing wave ratios (VSWRs) in the waveguide. Additionally, arcs can form in waveguides where dust or small metal chips are present. The proposed sensor consists of a fluorescent optical fiber lying along the corner of a waveguide. When arcing occurs in the waveguide, the fiber fluoresces brightly. Much of this fluorescence is guided by the fiber to detection optoelectronics located outside the waveguide. The optical signal can be used to shut down the microwave transmitter and prevent further damage to the components. In addition, a novel scheme allows the proposed sensor to accurately determine the location of the arcing so that dismantling a large portion of the waveguide can be avoided. This optical system will have no effect on waveguide transmission properties, and should be both more reliable and less expensive than acoustical detection techniques.