Abstract: A method and apparatus for detecting a fault, such as a break or crack in a fiber optic cable. A test device transmits into a first end of fiber bundle under test a first pulse of optical energy. The time duration and/or intensity of the pulse propagating through the fiber after being reflected back through the fiber are determined and stored in memory. At a later point in time this step is repeated with a second pulse. If the propagation time and/or intensity of the second pulse varies by greater than a predetermined amount from that of the first pulse an alarm condition is indicated. From the propagation time of the second pulse a length is calculated and provided to the user. This length corresponds to the location of the fault.

Abstract: A method and apparatus for distinguishing between fiber types having different dispersion characteristics and arbitrary lengths is disclosed. An optical pulse having a predetermined wavelength and predetermined time width is propagated through the fiber and then detected. The optical pulse after being fed through the fiber is measured at different wavelengths along with the length of the fiber. If the measured pulse is within a predetermined amount at the determined length, then fiber under test corresponds to a type having a first dispersion characteristic. If it is determined that the measured pulse is within a second amount, then the fiber under test corresponds to a type having a second dispersion characteristic. Alternately one or more optical pulses of arbitrary width each having different wavelengths after being propagated through the fiber under test is fed through a plurality of filters and detected.