Central cavity cable with a predetermined gap that facilitates opening of the outer sheath

#The present invention relates in general to optical cables, and more particularly to an optical cable having a central cavity that provides a predetermined gap between (1) an inner diameter of an outer sheath and (2) an outer diameter of the contents within the cable's central cavity. The gap prevents optical wave guides within the central cavity from being damaged upon opening the outer sheath.

#Central cavity cables are known in which optical fibers (or soft buffer tubes containing optical fibers) are provided in a core tube that extends along the axis of the cable. An outer sheath, which may or may not include armoring, surrounds the core tube. Although core tube cable designs are generally thought to be acceptable, they are not without shortcomings. The shortcomings are most apparent when considering conventional, cable opening techniques. A cable may need to be opened, for example, to perform optical fiber splicing.

#Cable opening involves penetrating through the outer sheath and the core tube in order to gain access to the optical fibers and soft buffer tubes. Two primary techniques are employed for removing the outer sheath. In the first technique, a user pulls on a ripcord that is interposed between the core tube and the outer sheath. When pulled with enough force, the ripcord cuts through the outer sheath. In the second technique, a user manipulates a cutting tool to penetrate through the outer sheath and partially into the core tube. That is, the cutting tool penetrates past the outer sheath's inner diameter and partially into the wall thickness of the core tube. Once the outer sheath is removed, the core tube is then opened to gain access to the central cavity in which the optical fibers and soft buffer tubes are provided.

#FIG. 1 is a perspective view of a cable according to an embodiment of the present invention;

#FIG. 2 is a perspective view of an optical wave guide provided in the cable shown in FIG. 1;

#FIG. 3(a) is a cross sectional view taken transverse to the longitudinal axis of the cable shown in FIG. 1, before being cut by a tool;

#FIG. 1 shows a cable 10 according to an embodiment of the present invention. The cable 10 has an outer sheath 40, which may or may not include an armoring 90. The outer sheath 40 defines a central cavity 130 along a longitudinal axis 50 of the cable 10. The central cavity 130 accommodates optical wave guides 20. The optical wave guides 20 are surrounded by a tape 30. The optical wave guides 20 and the tape 30 extend loosely through the central cavity 130.

#Turning briefly to FIG. 2, the optical wave guides 20 include soft buffer tubes 70 in which optical fibers 60 are provided. Alternatively, the optical wave guides 20 may include bare optical fibers 60 (without the soft buffer tubes 70). Such optical wave guides 20 are well known in this art, and therefore a detailed description of the same is not provided.

#In FIG. 3(a), the cable 10 is shown in a “pre-cut” state. That is, FIG. 3(a) shows the normal or expected positional relationships among the cable elements. Since the optical wave guides 20 and the tape 30 are loosely provided in the central cavity 130, the optical wave guides 20 may occupy any available space within the tape 30, and the tape 30 may occupy any available space around the optical wave guides 20. Moreover, it will be appreciated that the positional relationships among the cable elements within the central cavity 130 may vary along the longitudinal axis 50 of the cable. FIG. 3(a) also shows a cutting tool 100 positioned above the cable 10.