METHOD AND CIRCUIT DEVICE FOR CHECKING AN OPTICAL CABLE FOR THE PASSAGE OF LIGHT AND UNDUE INCREASES IN ATTENUATION CAUSED BY DEFECTS

摘要

Method and apparatus for detecting defects in an optical cable composed of a series of cable units. Light pulses are sent through one cable conductor and returned to the starting end via a second conductor and an electrical signal representative of the light intensity exiting the second conductor is derived. The electrical signal is applied to a sensitivity control circuit which is switched through a succession of sensitivity levels starting from a minimum level and proceeding to a maximum level. Each sensitivity level corresponds to the attenuation produced by a cable composed of a given number of cable units and is associated with a particular ratio between the output signal provided by the sensitivity control circuit and the elect tribal signal applied thereto. Switching continues until the output signal provided by the sensitivity control circuit exceeds a selected threshold value, and the number of levels through which the sensitivity control circuit has been switched until that output signal has been reached is displayed.