Optical waveguides – Accessories – External retainer/clamp
Reexamination Certificate
2002-10-15
2004-04-06
Healy, Brian (Department: 2874)
Optical waveguides
Accessories
External retainer/clamp
C385S136000, C385S100000, C385S053000
Reexamination Certificate
active
06718112
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates generally to the communications field, and, more particularly to a clip for securing and routing fiber optic cables on a printed circuit board (PCB) or other component used in the communications field.
B. Description of the Related Art
Presently, it is a problem in the field of communication cable installation to ensure the precise placement of the communication cable without the possibility of damage to the communication cable by the provision of tight bends, or inappropriate use of fasteners, or inadequate support to the communication cable. Such communication cables include conventional telephone cable having a plurality of copper conductors, coaxial cable, optical fiber, or the like. In all of these applications, the minimum radius of curvature of the communication cable is well defined, and bending the communication cable in a tighter bend can cause damage to the communication medium housed within the cable. The installer of communication cable is thus faced with the problem of routing the communication cable over surfaces, which typically include sharp bends, without over bending the communication cable, yet also securing the communication cable to these surfaces in a manner to ensure protection from damage.
This problem is further heightened when fiber optic cables are used. Glass fibers used in such cables are easily damaged when bent too sharply and require a minimum bend radius to operate within required performance specifications. The minimum bend radius of a fiber optic cable depends upon a variety of factors, including the signal handled by the fiber optic cable, the style of the fiber optic cable, and equipment to which to fiber optic cable is connected. For example, some fiber optic cables used for internal routing have a minimum bend radius of 0.75 inches, and some fiber optic cables used for external routing have a minimum bend radius of 1.0 inches.
Damaged fiber optic cables may lead to a reduction in the signal transmission quality of the cables. Accordingly, fiber optic cables are evaluated to determine their minimum bend radius. As long as a fiber optic cable is bent at a radius that is equal to or greater than the minimum bend radius, there should be no reduction in the transmission quality of the cable. If a fiber optic cable is bent at a radius below the minimum bend radius determined for such cable, there is a potential for a reduction in signal transmission quality through the bend. The greater a fiber optic cable is bent below its minimum bend radius, the greater the potential for breaking the fibers contained in the cable, and the shorter the life span of the cable.
Furthermore, the recent increase in bandwidth requirements for telecommunications systems has resulted in more densely packed equipment and fiber optic cables than prior systems. Many carriers or other consumers of optical communications equipment have a very limited floor space in which to place new equipment and fiber optic cables. For example, some carriers may only have a single open bay (or shelf) in which to place new equipment and fiber optic cables. If the communications equipment can be more densely packed, then a greater amount of equipment and fiber optic cables may be placed within the available space. Thus, it is even more necessary now to be able to bend fiber optic cables around corners and other obstacles in order to route the cables to and from equipment such as computers, connector panels, junction boxes, etc.
For example, in a telephone switching office, the various switching components are split onto different printed circuit boards (PCBs). Fiber optic cables may be used to route the signals between the different PCBs or between components on a single PCB. In a conventional arrangement, the PCB is generally placed in a shelf or rack alongside other such PCBs.
The fiber optic cables are used for transferring signals between reception ports and electro-optical converters provided on the PCB or PCBs. The fiber optic cables generally come in three and six foot lengths with connectors provided at the ends thereof However, the PCB may have a width of only several inches. To accommodate for the extra length of the fiber optic cables, such cables are routed around and secured to the PCB via a plurality of clips. The clips are secured to the PCB via holes drilled through the PCB, adhesive, or fasteners.
The fiber optic cables are generally routed, by hand, through the clips, without bending the fiber optic cables beyond the minimum bend radius. Whether this requirement is satisfied depends on the individual operator doing the assembly. The fiber optic cables ideally should be routed in to prevent stress being applied to the cables.
PCB assemblies are used in computers, communications equipment, televisions, and many other products. In a typical PCB assembly, many electrical components are attached to the top and bottom surfaces of a PCB. Since the electronics manufacturing industry is highly competitive, it is important to maximize the throughput of processing PCB assemblies and to securely attach functional electrical components to the PCBs.
The manufacturing of PCB assemblies involves many processes, one of which is surface mounting components to PCBs. In addition to maximizing the throughput of processing PCB assemblies, it is also becoming important to accurately mount a large number of very small components to one side of the PCB assemblies.
As disclosed in U.S. Pat. No. 6,426,880, the disclosure of which being incorporated herein by reference except where inconsistent with the present invention, surface mount technology (SMT) is a construction technique for electronic device assemblies in which the terminals of electronic devices are attached to the surface of a PCB, by solder or some other conductive adhesive. In SMT, the device terminals each have a flat (planar) contact surface that rests on corresponding conductive “landing pads” on the PCB surface. SMT may be distinguished from other construction techniques which generally employ “through pin” terminals on their electronic device packages. In these other construction techniques, the device terminals are pins which are placed in holes passing through the circuit board and sealed there by solder or some other conductive adhesive.
SMT fabrication permits components to be mounted to both sides of the PCB. As such, a primary advantage which SMT provides over “through pin” construction techniques is the increased packing density, i.e., the number of components on the PCB per unit of area, which may be achieved by mounting electronic devices on both sides of the PCB. In the “through pin” techniques, the terminal physically passes through a hole in the board, thereby providing a strong, shock resistant mechanical coupling to the board. In SMT, the terminals are physically coupled to the board only by conductive adhesive.
Conventional fiber optic cable clips or retention devices are problematic for at least three reasons. First, current clips require performance of secondary operations on the PCB, in addition to the SMT mounting of components on the PCB. Such secondary operations increase the risk of damage to the PCB. Second, the through holes, adhesives, and fasteners used to attach clips to the PCB also increase the chance of damage to the PCB. For example, forcing such clips onto PCBs could potentially warp or bend the PCB, which creates circuit trace damage to the PCB. Third, clips attached to PCBs via through holes tend to rotate in the holes, increasing the risk of damage to the fiber optic cables retained in the clips.
Thus, there is a need in the art to provide an inexpensive mechanism for securing and routing multiple fiber optic cables in the denser optical communications systems that may be easily customized by an operator and prevent the fiber optic cables from being damaged or bent beyond their minimum bend radii, and utilize existing PCB SMT techniques.
REFERENCES:
patent: 6005195 (1999-12-01), Kam
patent: 6215942 (2001-04-0
Harris David B.
Rodriguez Lou
Cammarata Michael R.
Ciena Corporation
Healy Brian
Olsen James M.
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