An obstacle detection system includes a first light emitter that emits a light signal and a first light detector configured to receive a portion of the light signal reflected back from an object. The obstacle detection system includes a second light emitter configured to emit a test signal toward the first light detector, and a second light detector configured to detect the light signal emitted by the first light emitter. The obstacle detection system includes a processor to determine, based on the light signal, whether an obstruction is detected and whether, by use of the second light emitter and the second light detector, the first light emitter and the first light detector are operable.