Optical fibers are used in an increasing number and variety of applications, such as a wide variety of telecommunications and data transmission applications. As a result, optical fibers must frequently be aligned and interconnected to permit optical signals to be coupled between the optical fibers with little attenuation. While a variety of techniques have been developed for reliably interconnecting individual optical fibers, multifiber cables or ribbons are being increasingly employed and must therefore be frequently interconnected to other multifiber cables or ribbons. As known to those skilled in the art, the interconnection of multifiber cables is significantly more challenging than the interconnection of individual optical fibers since each respective optical fiber of one multifiber cable must be simultaneously aligned with a corresponding optical fiber of the other multifiber cable. As explained below, the challenges presented by the interconnection of multifiber cables is further exacerbated in instances in which the multifiber cables are mounted upon the end portions of single mode optical fibers.
Conventional multifiber cables are interconnected by first mounting an appropriate multifiber ferrule upon the end portions of a plurality of optical fibers. For example, the DC ferrule supplied by Siecor Corporation of Hickory, N.C. can be mounted upon the end portions of two optical fibers, and the QC ferrule also provided by Siecor Corporation can be mounted upon the end portions of four optical fibers. After assembling the remainder of the multifiber connectors, the ferrules are inserted into opposed ends of an alignment sleeve which attempts to align the ferrules and, more particularly, the optical fibers upon which the ferrules are mounted. Some multifiber ferrules, such as the DC and QC ferrules, have opposed side surfaces that define lengthwise extending grooves. As such, the alignment sleeves may include a pair of diametrically opposed, lengthwise extending alignment ribs for engaging respective ones of the grooves defined by the ferrules. The engagement of the alignment ribs and the grooves defined by the ferrule serve to orient the ferrules and, more specifically, the optical fibers upon which the ferrules are mounted.
Modern applications are demanding ever increasing precision with respect to the alignment of optical fibers. In particular, increased alignment precision is demanded in instances in which single mode optical fibers are aligned in view of the extremely small size of the cores of the single mode optical fibers. As such, conventional alignment sleeves for aligning multifiber ferrules have not been entirely successful in aligning optical fibers and, in particular, single mode optical fibers requiring the demanded precision. In this regard, some alignment sleeves include integrally molded or otherwise integrally formed alignment ribs. As a result of the tolerances inherent in molding or other fabrication techniques, the alignment ribs may not be precisely positioned in a diametrically opposed relationship and may not extend perfectly parallel to each other and to the longitudinally axis defined by the alignment sleeve. As such, the alignment ribs may introduce at least some misalignment between the ferrules and, more particularly, between the individual optical fibers upon which the ferrules are mounted. Although this slight misalignment is generally acceptable for multimode applications, the interconnection of multiple single mode fibers demands greater alignment precision and may not tolerate such misalignment, albeit slight misalignment, in certain applications.
Another type of alignment sleeve is disclosed by U.S. Pat. No. 5,737,463 which issued Apr. 7, 1998 to Roger E. Weiss, et al. (hereinafter the "Weiss '463 patent"). The Weiss '463 patent discloses an alignment sleeve for receiving and aligning multifiber ferrules. Alignment members are held within the alignment sleeve such that the alignment members extend lengthwise along opposed interior side surfaces of the alignment sleeve. As such, the alignment members can engage the grooves defined by the opposed side surfaces of the multifiber ferrules in order to align the optical fibers upon which the multifiber ferrules are mounted. The alignment members are held within the alignment sleeve by hook portions which protrude through respective windows defined by the side surfaces of the alignment sleeve. In particular, the hook members engage corresponding reduced diameter portions of the alignment members such that the alignment members are held in place against the side surfaces of the alignment sleeve. As will be apparent, the alignment members described by the Weiss '463 patent must therefore be specially fabricated to include a pair of reduced diameter portions that have a predetermined depth, width and spacing.
Notwithstanding the various conventional alignment sleeves, including the alignment sleeve described by the Weiss '463 patent, a need still exist for alignment sleeves which will align a pair of multifiber ferrules and, more particularly, which will align the plurality of optical fibers upon which the multifiber ferrules are mounted with increased precision. In particular, a need exists for alignment sleeves which can align multifiber ferrules with the precision required to facilitate interconnection of a plurality of single mode optical fibers.