Exemplary embodiments of a flame detector and operating method. Optical energy is received at one or more optical sensors, and the detector processes the energy to determine whether the received energy is from a known remote test source. If so, the flame detector is operated in a test mode. If the processing indicates that the received optical energy is not a test signal, the flame detector is operated in a flame detection operating mode. The detector processing uses an artificial neural network in an exemplary embodiment in the flame detection operation mode.