Optical arc sensor for detecting an arc in an electrical installation comprising - a sensor housing having a housing base and a housing cover capable of being placed onto the housing base; - a first optical waveguide, one end of which is arranged within the sensor housing for the purpose of detecting a light signal generated by an arc; - a second optical waveguide, one end of which is arranged within the sensor housing for the purpose of emitting a test light signal, wherein the ends of the two optical waveguides (32, 33) that are arranged within the sensor housing are optically connected to one another; - the sensor housing has a guide, which guides the two optical waveguides (32, 33) within the sensor housing in such a way that their respective ends are arranged parallel to one another and in a manner directed directly towards one another in a light detection region; - the housing cover is embodied in a substantially flat fashion and has, in the region of the light detection region, an outwardly directed bulge configured from the same material as the housing cover; and - the guide is shaped in such a way that the ends facing away from those ends of the optical waveguides (32, 33) that are arranged within the sensor housing are guided out of the sensor housing at the same side of the sensor housing; - the guide is configured in such a way that both optical waveguides (32, 33) are axially symmetrical within the sensor housing and experience substantially the same curvature directed towards one another; characterized in that the bulge arranged in the housing cover is configured with regard to its material and/or its shaping such that it brings about a desired damping of a light signal that enters the light detection region from outside the sensor housing in such a way that only light signals having an initial light intensity that is characteristic of an arc enter the light detection region with a significant entry light intensity. - a sensor housing having a housing base and a housing cover capable of being placed onto the housing base; - a first optical waveguide, one end of which is arranged within the sensor housing for the purpose of detecting a light signal generated by an arc; - a second optical waveguide, one end of which is arranged within the sensor housing for the purpose of emitting a test light signal, wherein the ends of the two optical waveguides (32, 33) that are arranged within the sensor housing are optically connected to one another; - the sensor housing has a guide, which guides the two optical waveguides (32, 33) within the sensor housing in such a way that their respective ends are arranged parallel to one another and in a manner directed directly towards one another in a light detection region; - the housing cover is embodied in a substantially flat fashion and has, in the region of the light detection region, an outwardly directed bulge configured from the same material as the housing cover; and - the guide is shaped in such a way that the ends facing away from those ends of the optical waveguides (32, 33) that are arranged within the sensor housing are guided out of the sensor housing at the same side of the sensor housing; - the guide is configured in such a way that both optical waveguides (32, 33) are axially symmetrical within the sensor housing and experience substantially the same curvature directed towards one another;