Patent Application
20050276562
1. Field of the Invention
The present invention relates generally to a closure for interconnecting optical fibers, and more specifically, to a fiber optic closure with integral cable management and sealing features.
2. Description of the Related Art
Optical fiber cable is used for a variety of applications including voice communications, data transmission and the like. As a result of the increase in demand, fiber optic networks typically include an ever-increasing number of interconnection points in which one or more optical fibers of a distribution cable are interconnected with optical fibers of one or more drop cables. These interconnection points provide a convenient location for branching fiber optic drop cables to subscribers and may be used to supply “fiber-to-the-premises” (FTTP), “fiber-to-the-home” (FTTH) and “fiber-to-the-business” (FTTB), referred to generically as “FTTx”. Based on the increase in the number of interconnection points, and based on the locations of these points within a network (neighborhoods, etc), low volume, aesthetically pleasing closures are needed for protecting, handling, connecting and managing the optical fibers and fiber optic distribution and drop cables at the interconnection points. The closures should provide protection of the interconnection point as well as the accessed optical fibers and fiber optic cables from environmental influences, such as water intrusion, for example from wind-driven rain, and mechanical influences, such as stress.
With regard to aerial splice closures, there are several features that are typical in existing strand-mounted closures that the present invention improves. First, aerial splice closures typically require mid-span access to the distribution cable and most current strand-mounted closures are designed with two cable seals (one on each end of the closure) for the entrance and exit of distribution cable. Typically, separate seals are also provided for the entrance of the drop cables. By having multiple seals on the same closure, and by having the closure mounted along the strand as opposed to hanging below it, the difficulty of providing protection against water intrusion is increased. Second, the number of components needed for the multiple seals increases the complexity of the closure, increases the volume of the closure and increases the labor and time required to install the closure. Third, in addition to having multiple seals for the various cables, conventional splice closures typically use a molded or pre-formed gasket to seal the perimeter of the closure against water intrusion, which significantly increases the cost of the closure. Lastly, conventional closures do not provide integral cable management, but often require external cable routing guides that further increase the cost and complexity of the network and decrease the aesthetic benefit obtained from a slim profile, small volume closure.
To overcome these and other disadvantages, what is desired is a fiber optic closure having integral cable management and sealing features. What is also desired is a closure having a structure that allows the closure to hang below an aerial strand in such a way that a complex and costly seals are not necessary to prevent intrusion of wind driven rain into the closure. To further simplify the design of conventional closures, the improved closure should have a gasket-less seal around its periphery and have a cable routing contour that provides a natural drip loop for all cables routed into and out of the closure. By designing the closure in this way, it is not necessary to provide complex and costly cable seals for all cables entering and exiting the closure. To further improve upon current closure designs, and based on the recent emergence of “FTTx” networks, it is further desirable to provide a closure that not only includes all of the advantages described above, but also includes quick-connect drop cable ports that permit less experienced and less skilled technicians to perform optical connections and reconfigurations in the field a convenient mid-span access locations.
To achieve the foregoing and other objects, and in accordance with the purpose of the present invention as embodied and broadly described herein, the present invention provides various embodiments of fiber optic interconnection closures having integral cable management and sealing features. In one embodiment, the present invention provides a fiber optic interconnection closure comprising a base and a cover, wherein an outer periphery of the base defines a surface for routing a fiber optic distribution cable into a cable entry location defined by the base. In alternative embodiments, the interconnection closure may further comprise one or more of a funnel-shaped cable guiding feature, one or more cable routing tabs, one or more cable retention clips, one or more fiber routing guides, one or more fiber routing spools, a splice holder, or a grounding strip.
In another embodiment, the present invention provides a fiber optic interconnection closure comprising a base, a cover and at least one connector port located in an exterior wall of the base, wherein an outer periphery of the base defines a surface for routing a fiber optic distribution cable into a cable entry location defined by the base. In alternative embodiments, the interconnection closure may further comprise a funnel-shaped cable guiding feature, one or more fiber routing guides within the interior of the closure, one or more fiber routing spools, or a grounding strip on the back side of the base for grounding a conductive strength member of the distribution cable.
In yet another embodiment, the present invention provides a fiber optic communications network having a fiber optic distribution cable comprising a plurality of optical fibers and at least one mid-span access location along the length of the distribution cable for accessing and terminating preselected ones of the plurality of optical fibers, one or more fiber optic drop cables having one or more optical fibers optically connected to the terminated optical fibers of the distribution cable, and an interconnection closure comprising a base and a cover, wherein an outer periphery of the base defines a surface for routing the fiber optic distribution cable into a cable entry location defined by the base.
These and other features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, wherein:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These exemplary embodiments are provided so that this disclosure will be both thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numbers refer to like elements throughout the various drawings.
The present invention provides various embodiments of interconnection closures for connecting preselected optical fibers of a distribution cable to one or more optical fibers of one or more drop cables. In the exemplary embodiments shown and described throughout the specification, the interconnection closure is an aerial closure that is supported by and hangs below the distribution cable or an existing strand in a communications network. However, in alternative network deployments, the interconnection closure may also be pole-mounted, housed within a pedestal or housed within a vault. It is envisioned that features may be added to the back of the closure to allow for mounting to a pole or to the internal structure of a pedestal. In all of the various embodiments, the closure consists of a cover and a base that are secured together using one or more fasteners, such as screws. The base and cover are preferably made of a lightweight yet rigid material, such as formed aluminum or molded UV resistant plastic. Although not shown, the cover may be tethered to the base to prevent separation. The closure is mounted to the aerial strand and allows mid-span access to preselected, terminated optical fibers of the distribution cable and “express” (i.e., un-terminated) optical fibers of the distribution cable, as well as the optical fibers of the drop cables. The various embodiments of the present invention may be deployed in a “fiber-to-the-premises” (FTTP) communication network, or in any fiber optic network in which it is desired to access and interconnect optical fibers of a distribution cable with optical fibers of a secondary, branch or drop cable in any manner now known or hereafter devised.
Throughout the specification, the term “distribution cable” is intended to include all types of fiber optic cables comprising a plurality of optical fibers within a cable jacket including, but not limited to, loose tube, monotube, central tube, tight buffered, ribbon, flat dielectric drop and the like. In the exemplary embodiments shown and described herein, the distribution cable is a tubeless figure-eight distribution cable or a standard single tube (SST) figure-eight distribution cable available from Corning Cable Systems of Hickory, N.C. The figure-eight cable comprises an optical transmission component, a strength or “messenger” component, and a cable jacket. In this design, the optical transmission component and the messenger component are separated from each other via the cable jacket, resulting in a figure-eight cross sectional configuration in which the messenger component may be separated from the optical transmission component without compromising the cable jacket surrounding the optical transmission component. In one embodiment, the messenger component comprises a conductive (e.g., metallic) strength member that may be either solid or made up of a plurality of strands wrapped in a helical fashion. In an alternative embodiment, the distribution cable is dielectric and the messenger component comprises a glass-reinforced plastic (GRP). The optical transmission component of the distribution cable comprises one or more optical waveguides, preferably up to about thirty-six, and more preferably between about twelve and about twenty-four, either disposed within a central buffer tube (monotube) or disposed within the cable jacket (tubeless). The distribution cable may also comprise additional strength members that provide tensile strength and resistance to cable shrinkage. It is understood that other cable types may be used in conjunction with the present invention. The distribution cable is preferably designed to provide stable performance over a wide range of temperatures and to be compatible with any telecommunications grade optical fiber. As used herein, the term “optical fiber” is intended to include all types of single mode and multi-mode light waveguides, including one or more bare optical fibers, coated optical fibers, loose-tube optical fibers, tight-buffered optical fibers, ribbonized optical fibers or any other expedient for transmitting light signals.
In all embodiments shown, the interconnection closure is breathable and does not comprise a sealing gasket disposed around the periphery of the closure between the cover and base. The closure may comprise one or more vents used to reduce condensation within the closure as required for free breathing aerial closures. The cable seal area is protected from water intrusion, and in particular wind-driven rain, by being recessed within the upper portion of the closure and shielded by an exterior wall of the base, thus providing a baffle effect from the wind and thereby allowing the cable seals to meet less stringent environmental requirements. By hanging the closure below the strand and by the manner in which the cables are routed into and out of the closure, natural drip loops are provided to prevent water from flowing along the cables to the cable seal area. The interconnection closure has a slim profile, small volume and low build cost due its reduced part count. In addition, because the closure design has only one protected cable seal area, a single, less robust cable seal is sufficient for all cables, despite the direction from which the cables are routed into the closure.
Referring now to
The base 22 defines a funnel-shaped cable guiding feature 36 and a cable routing feature 38, with both features being operable for guiding and routing the distribution cable and drop cables around the periphery of the closure 20, while maintaining the minimum bend radius of the cable. Each feature 36, 38 comprises an L-shaped flange that captures and guides the cables. As shown, the flanges may be provided with stiffening ribs. A lip 48 of the cover 24 extends over the cable routing feature 38 when the cover is in the closed configuration. Lances (not shown) may be provided along the periphery of the base 22 for strain relieving the cables using cable ties, wraps or clamps. The features 36, 38 further provide stabilization of the cables during installation. The outer periphery of the base 22 curves inwardly on one end to form a cable entry location 40. A plurality of fingers or tabs 42 guide the cables into the cable seal area 44. In a preferred embodiment, the closure 20 is oriented with the major axis of the elliptical base 22 generally parallel to the aerial strand and hangs below the strand to prevent water from running along the cables into the closure 20. The cable seal area 44 comprises two sets of tooth-shaped cable retention clips 46 for retaining and aligning the cables. The size of the spaces provided on the retention clips 46 may be varied whether a distribution cable or a drop cable is routed through a particular slot. The cables may be snapped into the retention clips 46 and held in place during installation. The cable seal area 44 comprises a foam, gel, rubber or like sealing material positioned between the pair of retention clips 46 operable for providing a compression seal. The retention clips 46 align the cables at the cable seal area 44 and insure sufficient compression of the cable sealing material on each cable. The cable sealing material is retained within the closure 20 in the cable seal area 44 when the cover 24 is secured to the base 22 so that the cable sealing material compresses the cables as the cover 24 is closed.
Referring now to
Referring to
After entering the interior of the closure 20 through the cable seal area 44, the cable jacket 60 is preferably ring cut and removed from the portion of distribution cable 54 that is routed within the closure 20. The end of the cable jacket 60 adjacent the ring cut may be strain relieved in a known manner. The transport tube 66 is likewise ring cut and removed from the optical fibers 68 of the distribution cable 54 routed within the closure 20. The cable jacket 60 and the transport tube 66 may be simultaneously ring-cut and removed from the portion of the distribution cable 54 routed within the closure 20, as is well known in the art. The transport tube 66 may also be strain relieved in a known manner at or slightly beyond the cable seal area 44. The length of cable jacket 60 and transport tube 66 removed from the distribution cable 54 is preferably up to about 36 inches, more preferably up to about 24 inches. In alternative embodiments, the length of the cable jacket 60 and transport tube 66 that is removed may vary without departing from the scope of the invention. The locations of the ring cuts relative to the cable seal area 44 may also vary without departing from the scope of the invention. As shown, the incoming distribution cable 54 is routed into the cable seal area 44 adjacent the second tab 42 from the top, and the outgoing distribution cable 54 is routed out of the cable seal area 44 adjacent the top tab 42.
The optical fibers 68 of the distribution cable 54 are routed around fiber routing guides 69 to the first (right-hand as seen in
Referring to
As with the distribution cable 54 described above, after passing through the cable seal area 44, the cable jackets 60 and the transport tubes 66 of the drop cables 74 are preferably ring cut, terminated and strain relieved in a known manner. The length of cable jacket 60 and transport tube 66 removed from the drop cables 74 is preferably up to about 36 inches, more preferably up to about 24 inches. In alternative embodiments, the length of the cable jacket and transport tube removed and the points of removal may vary without departing from the scope of the invention. As shown, the drop cables 74 entering the closure 20 are routed into the cable seal area 44 adjacent the lower tabs 42.
A predetermined amount of slack optical fibers 68 of the drop cables 74 is routed in a convenient figure-eight pattern around the two routing spools 32 and into the right-hand side of the splice holder 34. By having two routing spools 32, it is possible to wrap the slack optical fiber in either clockwise or counterclockwise directions around each routing spool 32 to obtain a desired entry orientation into the splice holder 34 and to store a desired amount of slack. A predetermined number, and typically all, of the optical fibers 68 of the drop cables 74 are routed into the splice holder 34. In the preferred embodiment, the optical fibers 68 of the drop cables 74 are routed such that the ends of the optical fibers 68 enter the splice holder 34 opposite the ends of the optical fibers 70 of the distribution cable 54 terminated within the closure 20.
Referring to
Referring to
The closure 20 is shown in
Referring to
As with the previous embodiment, after entering the closure 20 through the cable seal area 44, the cable jacket 60 and the transport tube 66 are ring cut and removed from the portion of distribution cable 54 routed within the closure 20. The cable jacket 60 and the transport tube 66 may be strain relieved adjacent the ring cut in any known manner at or beyond the cable seal area 44. The length of cable jacket 60 and transport tube 66 removed from the distribution cable is preferably up to about 36 inches, more preferably up to about 24 inches. In alternative embodiments, the length of the cable jacket 60 and transport tube 66 removed may vary without departing from the scope of the invention. The locations of the ring cuts relative to the cable seal area 44 may also vary without departing from the scope of the invention. As shown, the incoming distribution cable 54 is routed into the cable seal area 44 adjacent the second tab 42 from the top, and the outgoing distribution cable 54 is routed out of the cable seal area 44 adjacent the top tab 42.
The optical fibers 68 of the distribution cable 54 are routed around fiber routing guides 69 and onto the routing spool 32. However, in an alternative embodiment, the fiber routing guides 69 may not be present and the optical fibers 68 may be routed directly to the routing spool 32. A predetermined amount of slack optical fiber 68 is routed around the routing spool 32 in a preferred direction and into the splice holder 34. As previously described, a predetermined number of the optical fibers 70 are terminated and routed into the splice holder 34. Preferably, the ends of the terminated optical fibers 70 of the distribution cable 54 are routed such that they enter the splice holder 34 opposite the ends of the pigtails. The express (i.e., un-terminated) optical fibers 68 of the distribution cable 54 are routed around the routing spool 32 and if desired around the fiber routing guides 69 to exit the closure 20 via the cable seal area 44. The cable jacket 60 and the transport tube 66 of the outgoing distribution cable 54 begin again prior to entering the cable seal area 44 from the interior of the closure 20. The outgoing distribution cable 54 is routed through its appropriate tab 42 and exits the closure 20 via the cable entry location 40. The distribution cable 54 is then routed around the periphery of the closure 20 through the cable routing feature 38 and the funnel-shaped cable guiding feature 36 in the downstream (i.e., subscriber) direction, where another preselected set 70 of optical fibers 68 of the distribution cable 54 may be terminated within another interconnection closure 20.
Referring to
The foregoing is a description of various embodiments of the invention that are given here by way of example only. Although fiber optic interconnection closures with integral cable management and sealing features have been described with reference to preferred embodiments and examples thereof, other embodiments and examples may perform similar functions and/or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the claims appended hereto.
