Abstract:
A shelf assembly and system, which reduces the potential for accidental disruption of service or damage to neighboring transmission elements in a telecommunications network. The present invention operates to guide the transmission elements or fiber cables to and/or from a mounting position, and in or out from either side of electrical and/or optical telecommunications equipment. Fiber cables coupled at the mounting positions can be directed through reversible and removable fiber channels. Each fiber channel has a smooth surface and a radius of curvature, which provides an appropriate bend radius for guiding, routing, or bending the fiber cables into a fiber trough.

Description:
BACKGROUND OF THE INVENTION 
     Most modern equipment for implementing telecommunications systems contain one or more electronic apparatus housed in a casing. For example, optical switches can hold multiple, closely spaced, optical cards, enclosed in a casing having a front access door, side walls, and a backplane. Generally, at one end, the optical cards are electrically coupled to the backplane, which performs an interconnect function between the various cards within the casing. In most instances, the optical cards terminate at the other end with connectors for fiber optic cables. The close arrangement of the optics cards and fiber cables within the casing provides a space savings and the advantage of allowing the cards and cables to be removed/inserted independent of one another. 
     Unfortunately, there are drawbacks to the closely spaced card/fiber cable arrangement, as well. For example, fiber cables are at risk when service work is performed on the equipment, such as installation/removal of cards or fiber cables and/or replacement of equipment components, such as fans, filters, and the like. The fiber cables are typically allowed to dangle from the casing and may become easily dislodged, which may cause unwanted disruption in the service being provided by the equipment. The fiber cables may also become entangled with other equipment systems, which may pose a hazard to technicians and others who work in close proximity to the equipment system. Finally, because of the dangling nature of the fiber cables, undue strain may be placed on the fiber cables, which may cause them to become dislodged, to be chaffed against sharp edges, or else to break. 
     Installers of optical switching equipment have encountered other drawbacks when routing fiber cables into and out from optical switches. For example, it is often necessary to route fiber cables about sharp corners. Routing fiber cables around sharp corners is inherently problematic, since over time, any movement of the fiber cable relative to the sharp corner may cause chaffing and/or cuts to develop in the fiber cable. It also happens that fiber cables are pulled on during installation or repair with sufficient force so as to deform the fiber cable. Unfortunately, when fiber cables are bent beyond a certain limit (i.e. bend radius) or pulled on with sufficient force, the fiber cable can break or the signal traveling through the cable may be attenuated beyond acceptable operational limits. 
     SUMMARY OF THE INVENTION 
     The present invention provides a shelf assembly and system, which reduces the potential for accidental disruption of service or damage to neighboring transmission elements in a telecommunications network. The present invention is useful for guiding incoming or outgoing transmission elements, such as optical fiber cables, to and from the telecommunications network. The present invention operates to guide the fiber cables to or from a mounting position, and in or out from either side of electrical and/or optical telecommunications equipment. 
     The shelf assembly can include a card cage assembly, which defines an interior space for receiving plug-in cards, generally having telecommunications functionality. Each plug-in card includes at least one fiber cable mounting position disposed at a terminal end of the card. Fiber cables coupled at the mounting positions can be directed through reversible and removable fiber channels. In accordance with the present invention, each fiber channel has a smooth surface and a radius of curvature, which provides an appropriate bend radius for guiding, routing, or bending the fiber cables into a fiber trough. The fiber trough provides a pathway to openings at either side of the shelf assembly. Advantageously, at the open ends of the fiber trough are fiber guide devices, which provide a smooth, rounded exit/entry openings through which fiber cables are introduced into the shelf assembly. Advantageously, fiber reels can be disposed on an external portion of the card cage assembly, such that the fiber cables can be stored. 
     The present invention has many advantages, such as simultaneous bi-directional access and routing to the plug-in cards in the system, while maintaining an appropriate bend radius for each fiber cable. The smooth concave surface of the fiber channels as well as the smooth, rounded surface of the fiber guide device reduces the possibility of chaffing or cutting of the fiber cables during operations or servicing of the equipment. The fiber channels and the fiber guide are modular and removable, which allows for simple redirecting of the fiber cables within the fiber trough and avoids the need to locate the fiber cables along a tortuous path to reach the mounting positions. The present invention also allows a technician the ability to access components within the card cage assembly without crossing the fiber cable paths and therefore minimizes the potential for service disruptions. 
     Other uses, advantages, and variations of the present invention will be apparent to one of ordinary skill in the art upon reading this disclosure and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the fiber shelf assembly of the present invention; 
     FIG. 2 is a magnified view of a portion of the shelf assembly of FIG. 1; 
     FIG. 3A is a simplified side view of the fiber channels of the present invention, and FIG. 3B is a simplified cross-sectional view of a single fiber channel mounted to the fiber shelf assembly of FIG. 1; and 
     FIG. 4 is a simplified side view of the shelf assembly of FIG.  1 . 
     FIGS. 5A and 5B are simplified front and side views of the shelf assembly system of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a fiber shelf assembly  5 , which provides for connecting optical fibers of optical cables  7  to plug-in cards (not shown) having telecommunications functionality, such as for optical switching. Fiber shelf assembly  5  includes card cage assembly  10 , for receiving vertically spaced apart plug-in cards, which terminate at a mounting position  11 , having horizontally in-series spaced fiber cable mounts or terminals  13 . 
     Card cage assembly  10  includes a housing or main chassis  12 , having several components, such as top wall  14 , bottom wall  16 , side wall  18 , side wall  20 , back wall  22 , and a front access door  24 . Depending on the embodiment, chassis  12  may have mounting fixtures  26  and  28  located on the side walls  18  and  20  of chassis  12  to facilitate the mounting of assembly  10 . Chassis  12  and mounting fixtures  26  and  28  may be made with sheet metal, injection molded plastic, or other similarly suited structural materials. 
     Chassis  12  defines an interior cavity or space  30 . Interior cavity  30  is suitable for removably receiving one or more electronic apparatuses. In one embodiment, interior cavity  30  can be large enough to be capable of removably receiving electronic apparatuses, such as modules, PCAs, or other types of plug-in cards, which may provide a telecommunications functionality to shelf assembly  5 . Front access door  24  provides access to interior cavity  30  for replacement, removal, assembly, servicing, and/or repair of the electronic apparatuses. Optionally, top and bottom walls  14  and  16  and back wall  22  may have a universal mounting  32 , including slots or grooves used to support, guide, and align the plug-in cards while housed in interior cavity  30 . 
     FIG. 2 is a magnified view of a bottom portion of fiber shelf assembly  5  showing a plurality of fiber channels  34 , fiber trough  36 , and fiber guide  38  in accordance with an embodiment of the present invention. As shown, fiber trough  36  extends the length of card cage assembly  10 , along a bottom portion of the cage assembly. Fiber trough  36  provides a pathway for fiber cables routed to and from openings  40  and mounting positions  11  (FIG.  1 ). Accordingly, fiber trough  36  is sized to hold a plurality of fiber cables. Fiber trough  36  is enclosed with a fiber trough door  46 . Fiber trough door  46  can be pivotally coupled to card cage assembly  10  using a conventional pivoting means, such as a hinge. Optionally, the hinge may be spring loaded, such that trough door  46  can close automatically. Trough door  46  protects the fiber cables being routed through fiber trough  36  and provides ease of access to the fiber cables. 
     Fiber guides  38  at the end of fiber trough  36  can be mounted on, or fabricated directly into, each side wall  18  and  20 . Fiber guides  38  define and maintain openings  40  allowing fiber cables to be fed into or out from fiber trough  36 . As illustrated in FIGS. 2 and 4, fiber guide  38  may have a square donut shape, with center hole or opening  40 , and with a portion removed to allow fiber cables to be moved in and out of the fiber guide opening. Each fiber guide  38  can be formed on either end of fiber trough  36 , on a portion of side walls  18  and  20 . The internal surface  50  of fiber guide  38  is a cylindrical surface, made smooth to ensure that the fiber cables exiting or entering fiber trough  36  are not damaged or bent beyond acceptable limits. Accordingly, cylindrical surface  50  of fiber guide  38  can have a radius appropriate for whatever type of fiber cable is selected for use with fiber shelf assembly  5 . In one embodiment, the radius of internal surface  50  is about 25 mm to about 28 mm. Since fiber guide  38  is formed at both side walls  18  and  20 , fiber cables may be routed in or out of shelf assembly  5  from either side. Opening  40  can be any size appropriate for allowing numerous branches of fiber cables to exit/enter fiber trough  36 . Typically, opening  40  can be approximately 34 mm×21 mm. Optionally, if fiber guide  38  is removed, opening  40  can be about 34 mm×35.5 mm. Fiber guide  38  can be pressed, rolled, extruded, or molded from sheet metal, plastic, and the like, using conventional fabrication techniques. 
     A plurality of fiber channels  34  are disposed in fiber trough  36  and are used to guide fiber cables from mounting positions  11  (FIG. 1) and into fiber trough  36  with an appropriate curved orientation. The curved orientation of each fiber channel  34  is selected to direct the fiber cables along fiber trough  36  toward openings  40 . As shown in FIG. 2, fiber channels  34  extend into trough  36  and are positioned vertically in-series to correspond with a particular mounting position  11 . The curved surfaces of fiber channels can be directed to either end of fiber trough  36 . In one embodiment, at least half of the plurality of fiber channels  34  can be positioned to direct fibers toward one opening and the other half can be positioned to direct fibers towards the other end. Optionally, any number of fiber channels  34  can be made to direct fiber cables toward either opening  40 . 
     Fiber channels  34  are curved to ensure that a proper curved orientation is provided with a minimum bend radius not to exceed a preselected curvature. For clarity a single fiber channel  34  is shown in FIG. 3A to illustrate the curvature and spacing of each fiber channel  34 . Typically, the minimal bend radius for a fiber cable is a standardized value, which depends on the type of fiber cable. The curvature of fiber channels  34  can be designed to adhere to these standards for a preselected type of fiber cable. In accordance with these standards, for example, using a 3 mm type of fiber cable, the radius of curvature β should be approximately 30 mm; and using a 2.5 mm type of fiber cable, the radius of curvature β should be about 25 mm. In one embodiment, to ensure that an appropriate number of fiber cables can pass between each fiber channel  34 , each fiber channel  34  in a series of channels  34  should be separated on center a length α of between about 21 mm and about 26 mm. For example, when using 8 of the 3 mm type fiber cables, the distance α should be about 25 mm. 
     FIG. 3B is a simplified illustration of an isolated single fiber channel  34 , which shows how each fiber channel  34  is mounted in trough  36 . As shown in FIG. 3B, a fiber channel  34  is mounted to a bottom portion of cage assembly  10  using a conventional mounting means  33 , such as screws, rivets, welds, and the like. Each fiber channel can be made from any lightweight, average strength material, such as plastic, using conventional fabrication processes, including injection molding. The edges of each fiber channel  34  are kept smooth so as to avoid damaging the fiber cables. 
     FIG. 4 is a simplified side view of fiber shelf assembly  5 , which shows fiber reels  44  and  45 . Fiber shelf assembly  5  is broadly symmetrical about a centerline and, thus, the description of fiber reels  44  and  45  is directed to only one side of fiber shelf assembly  5  (e.g. side wall  18 ), with reference to the other side, only when necessary to describe a feature of the invention, since it is understood that the other end is structurally and functionally the same. 
     Fiber reels  44  and  45  are disposed on an external portion of side wall  18  proximate to fiber guide  38 . In this embodiment, fiber reels  44  and  45  are positioned above and below one another, so that excess fiber cable may be wrapped around fiber reels  44  and  45  and stored. Optionally, fiber reels  44  and  45  may be positioned side-by-side. Fiber reels  44  and  45  have rounded cylindrical surfaces to ensure that the fiber cable is kept in a curved orientation which does not bend the fiber cables beyond acceptable limits. In one embodiment, the rounded portions of fiber reels  44  and  45  have a radius appropriate for whatever type of fiber cable is used with fiber shelf assembly  5 . Fiber reels  44  and  45  can be spaced apart a distance λ, which ensures that the minimal bend radius for the fiber cable is not exceeded. In one embodiment, the distance λ is between about 130 mm and about 150 mm; for example about 140 mm. Fiber reels  44  and  45  can be made from any structural material and may be formed using conventional fabrication processes. For example, fiber reels  44  and  45  may be made of plastic or light structural metals and may be machined, pressed, or molded. Reels  44  and  45  are mounted using conventional means, such as sheet metal screws or rivets. 
     FIGS. 5A and 5B are simplified elevation and side views, respectively, of the system of the present invention. Shelf system  60  includes a card cage assembly  10 , a plurality of fiber channels  34 , a fiber guide  38 , and first and second fiber reels  44  and  45 . As illustrated in FIG. 5A, a transmission element  42 , such as a fiber cable, is operatively coupled at mounting position  59  to a plug-in card  62 , which may provide a telecommunications functionality to shelf system  60 . Fiber cables  42  are threaded down from mounting position  59  along the end of card  62  to fiber trough  36 . A fiber channel  34  disposed in fiber trough  36  urges fiber cables  42  to bend with a preselected bend radius, such that fiber cables  42  are guided into fiber trough  36 . Fiber cables  42  are then threaded along fiber trough  36  toward one side wall of shelf assembly system  60 , in this embodiment, side wall  18 . Once fiber cables  42  reach side wall  18 , they can be threaded out of card cage assembly  10  through opening  40  in fiber guide  38 . Fiber cables  42  can then be operatively coupled to various electronic devices, as desired. 
     In one embodiment, when for example shelf system  60  is non-operative, it may be necessary to store fiber cables  42 . As shown in FIG. 5B, fiber cables  42  can be routed from opening  40  to engage fiber reels  44  and  45  to be appropriately wrapped or coiled and stored, while maintaining an appropriate bend radius. 
     FIG. 5B also illustrates two optional components of the present invention. A bend radius retainer  64  can be used on fiber cables  42  to maintain a desired bend radius after fiber cable  42  is coupled to mounting position  59  and made to extend out and bend down toward fiber trough  36 . Retainer  64  ensures that fiber cables  42  are not kinked or bent beyond acceptable limits at this juncture. Bend radius retainer  64  can be made of any structural material that has appropriate strength to maintain a preset curvature in a fiber cable. For example, retainer  64  may be made of an injection molded plastic or nylon. 
     Once fiber cables  42  are threaded down the end of card  62 , the fiber cables may be held bunched together using a retaining clip  66 . Retaining clip  66  may be mounted, for example, onto the end portion of card  62 . In one embodiment, retaining clip  66  includes a ring and stem arrangement, where the stem is mounted to card  62  and extends the ring outward into the fiber cable path, such that fiber cables  42  can be threaded through the ring and held together. Optionally, the ring of retaining clip  66  can be made with a cinching mechanism, which can be used to cinch cables  42  together to keep the cables from straying away. Retaining clip  66  can be made of any suitable structural material, such as injection molded plastic or nylon. 
     The description of the invention given above is provided for purposes of illustration and is not intended to be limiting. The invention is set forth in the following claims.