the first row a blinking light in the first row a twice blinking light in the third row and so on the particular combination of a rhythmic pattern and a color defines a port signature associated with a fiber port 14 as a result when the apparatus 10 is powered on it is a straightforward matter to identify each fiber port 14 by its port signature referring now to fig4 a control system 34 for controlling the port lamps 18 features plurality of programmable timers 36 each of which has been preset to implement a particular rhythmic pattern each timer 36 controls all port lamps 18 that are in a particular timer 36 in fig2 a suitable timer 36 is the 555 timer first introduced by signetics corporation in 1971 but now available from a variety of manufacturers as an integrated circuit in operation one attaches to each fiber port 14 a first end of an optical fiber 19 then one turns on the port lamps 18 because each port lamp 18 displays a unique combination of color and rhythmic pattern one can inspect the second ends of each fiber and identify which second end corresponds to which first end this greatly facilitates for example identifying a fiber with a discontinuity or determining the second end of a fiber that corresponds to a particular first end a variety of rhythmic patterns can be used as a port signature or a part thereof in one embodiment the rhythmic pattern includes having a port.