A dust cap and a dust plug for installation with optical fiber connectors and optical fiber adapters respectively. The dust cap and the dust plug have features that protect an optical interface on the optical fiber connector and the optical fiber adapter from contamination. At least an exterior portion of the dust cap and the dust plug illuminate when installed on the optical fiber connector and the optical fiber adapter terminating an optical fiber transmitting visible light. The dust cap and the dust plug have features that reduce the intensity of a high power optical signal emitted from the optical fiber terminated by the optical fiber connector and optical fiber adapter. A first embodiment diffracts the optical signal, thereby reducing its intensity. A second embodiment disburses the optical signal, thereby reducing its intensity. A third embodiment absorbs high power frequencies of the optical signal and transmits certain visible frequencies. The dust cap and the dust plug function as a safe, visual fiber optic circuit continuity detector.