Fiber optic attenuation simulator

#Fiber optic cable of significant length (e.g., 500-5000 meters) is presently being put into use for data and communication links among other things. As with electrical cable, it is often necessary to test and evaluate the cables for continuity and attenuation during manufacturing, as installed, or while in use. Continuity meters which measure line loss in decibels have been developed and put to use. Such meters function by passing light from a source of known intensity through the fiber optic cable under test and comparing the intensity of the light received to the known intensity of the light transmitted from the source to determine line losses due to attenuation. Attenuation losses are usually measured in relative quantities such as decibels.

#A continuity or attenuation meter, like any other test instrument, must be calibrated. Heretofore, the calibration procedure has required that it be connected to a set of fiber optic cables of known length so that the continuity meter can be calibrated across its full range. This has meant retaining large lengths of standardized cable in the laboratory or taking the meter into the field for connection to cables of known length and attenuation. Such procedures are obviously inconvenient because they require either the storage of bulky cables or the inconvenience of having to transport the meter to be a remote site for calibration. In both instances, a number of standard length test cables must be connected and disconnected from the continuity meter. Thus, the test is not continuous across the full scale range of the meter.

#Sometimes it is desirable to simulate the normal attenuation of a fiber optic cable of definite length for evaluation of an optical communication system. Therefore, there is a need for an instrument that will simulate fiber optic tables of definite length rather than use standard length test cables.

#For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

#FIG. 1 is an isometric view of the fiber optic attenuation simulator with the enclosure cover removed.

#FIG. 2 is a side elevation section taken along the line 2--2 in FIG. 1.

#Referring to the drawings in detail, wherein the numerals indicate like elements, there is shown a fiber optic attenuation simulator designated generally by the numeral 10 in FIG. 1.

#As shown, the fiber optic attenuation simulator 10 includes a principal support 12 fixed by threaded fasteners or the like to the base plate 14 which together with the cover 18 (see FIGS. 2, 3 and 4) defines a light and dust tight enclosure for the apparatus 10. The cover 18 is removably fixed to base plate 14 so as to substantially exclude ambient light. For the purpose of this invention, it has been found sufficient to attach the cover 18 to the plate 14 by means of threaded fasteners 20 extendigng through the integral cover flanges 21.

#As shown, the principal support 12 is in the form of a yoke comprising a base 15 and upstanding legs 17 and 19 which preferably are integral with the base 15 so that the entire principal support 12 provides a solid, rigid support for the apparatus 10. By way of example but not limitation, the principal support 12 may be manufactured from a single piece of aluminum with the base 15 being 3.0.times.6.12.times.0.250 inches and the legs 17 and 19 being 3.0.times.1.375.times.0.375 inches. The principal support 12 is fixed to the base plate 14 by threaded fasteners 16.