repeated after a predetermined time period until the interrogation mode is enabled referring to fig5 there is shown the interrogation mode having steps 100 128 in step 100 the internal counters in unit 30 are reset in step 102 laser 40 is turned on and a pulse is sent through optical device 34 to the fibers in bundle 16 next in step 104 the one of units 48a 48h corresponding to the fiber that is to be tested is enabled in step 106 the logic unit monitors its a d circuit 60 for the intensity of the received pulse reflected in the fiber while simultaneously counting the clock ticks in step 108 in step 110 the magnitude of the received pulse by a d circuitry 60 is stored in a memory and compared to the intensity recorded in step 87 in step 111 the processor determines if the intensity is within a 34 y 34 predetermined amount if it is the processor executes step 123 where the interrogation mode process restarts a predetermined amount of time later if it is not the processor 30 executes step 117 in step 117 the processor sends an indication of the intensity stored in step 110 to the headend 12 or provides an indication on display 32 of apparatus 14.