Optical fiber cable development, wherein the cable is capable of multichannel transmission, has led to a number of different cable configurations, prominent among which are bonded arrays of fibers forming a planar ribbon, and stacks of such ribbons within a core tube or sheath. In a typical ribbon array, a plurality of fibers, e.g., twelve, are held in spaced position parallel to each other by a suitable matrix, a configuration which simplifies construction, installation, and maintenance by eliminating the need for handling individual fibers. Thus, the splicing and connecting of the individual fibers can be accomplished by splicing and connecting the much larger ribbons provided that the fiber positions in the ribbon are precisely fixed and maintained.
In U.S. Pat. No. 4,900,126 of Jackson, et al., there is shown a bonded optical fiber ribbon which typifies, in many respects, the present state of the art for fiber ribbon. The ribbon comprises a plurality of longitudinally extending coated optical fibers disposed in a parallel array. A matrix bonding material fills interstices between adjacent fibers and extends about the array to form substantially flat protective surfaces. The ribbon may contain a large number of fibers such as, for example, sixteen, or it may have more or less, depending upon the particular application.
Cabling of fiber ribbon is usually accomplished by stacking a number of ribbons on top of each other and enclosing them loosely in a tube configuration while imparting a helical twist to the stack such as is shown in "A Modular Ribbon Design for Increased Packing Density of Fiber Optic Cables" by K. W. Jackson, et al., International Wire & Cable Symposium Proceedings 1993, pp. 20-26. In the manufacture of such a loose tube stacked ribbon configuration, the finished cable is wound upon a reel for storage and shipment. Quality control usually dictates that the transmission characteristics of such a cable wound upon a reel be measured for the cable in its reeled or storage condition. It has been found that in a reeled cable configuration, i.e., the fibers in the ribbon stack, exhibit a higher attenuation than does the same cable when laid out in a straight line configuration. Thus, it sometimes happens that a wound or reeled cable is rejected because of too high attenuation, when, in actuality, the cable in use would have an attenuation that was well within acceptable limits. This artificial packaging induced loss becomes greatly exacerbated with higher fiber count cables that are larger in sheath diameter. Such an increase in attenuation is attributable, therefore, to the winding of the cable on a drum, and is not predictable. That is, the increase may, in some instances, be large, while in other cases it is small. Thus, correlation of the attenuation increase with the size of the storage drum and the physical characteristics of the cable is difficult and unreliable. As a consequence, one cannot derive a precise "increased attenuation factor". Short of measuring cable attenuation with the cable in a straight-line configuration, which is totally impractical for the lengths of cable involved, it is desirable that a means be found for minimizing the transient increase in attenuation of fibers in a typical reel configuration.
A similar problem can arises when an optical fiber, buffered fiber, or ribbon, such as dispersion compensating fiber, is wound upon a drum or reel. Such fiber, wound upon a conventional reel, exhibits greater or higher loss than when the fiber is laid out straight. This too is a result of the compressive forces placed on the fiber in wound condition. In dispersion compensating fiber, the fiber usually remains upon the reel in use, hence, an extra component of lose is introduced into the active circuitry.