Disclosed is an optical fiber overheat detection testing apparatus including an optical fiber having a first end and a second end, the optical fiber having a predetermined length associated with a predetermined attenuation based on an overheat detection instrument loop. The apparatus includes a first interrupt disposed equidistant between the first end and the second end defining a first half of the optical fiber and a second half of the optical fiber, the first half and the second half having equal length, the first interrupt having a first actuator operable by a first electric current to attenuate light wave traversal of the optical fiber. The apparatus includes a second interrupt disposed on the first half and spaced from the first end at least six tenths of a meter, the second interrupt having a second actuator operable by a second electric current to attenuate light wave traversal of the optical fiber.