Abstract:
The challenge of pulling an optical fiber having a connector at its terminal end without incurring damage to the fiber or connector due to excessive pulling or bending is met by introducing a breakaway feature that disconnects the connectorized fiber from the pulling mechanism upon detecting excessive force. The breakaway feature may be positioned at several locations along the pathway connecting the optical fiber and the pulling force. In one embodiment the breakaway feature is disposed on a cover over the connectorized front end of the optical fiber. In other embodiments the breakaway element is inserted along the cord connecting the connectorized optical fiber to the pulling force.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to mechanisms to prevent damage to optical fibers when pulling forces are applied and, in particular, to a breakaway feature that disconnects a connectorized optical fiber from an excessive pulling force. 
     BACKGROUND 
     It is often necessary to install or modify optical fiber connections within a cabinet enclosure or other confined space. An optical fiber may be required to ultimately interact with more distant equipment, requiring the fiber or an intermediary optical fiber to be pulled and bent through the architecture of the enclosure or even through a wall. As with most optical fiber manipulations, it is essential to protect the integrity of the optical fibers and their terminal connectors from excessive forces such as bending or pulling during routing and placement. 
     Applications such as telecommunications, data processing, and data storage employ fiber optic jumper cables as intermediaries when connecting a fiber optic circuit with external equipment. Fiber optic jumper cables are generally a single strand of optical fiber having a connector mounted on its terminal end, but may also be a plurality of optical fibers, and are designed to interconnect two other fiber optic devices or cables within a transmission system. For example, fiber optic jumper cables may connect the front side of a fiber optic patch panel to another patch panel or some other enclosure. In connecting these components, the fiber optic jumper cable is often pulled around other patch panels in very limited spaces by applying a pulling device to the connector on the terminal end of the optical fiber. There are also instances in which an optical fiber having a connector, and not specifically a fiber optic jumper cable, must be routed through a complex enclosure or through a wall. 
     Routing optical fibers in confined areas requires consideration of the pulling forces applied to a fiber and its terminal connector, as well as potential excessive fiber bending. Pulling grips or other means for applying force may provide appropriate tension to guide the front end of an optical fiber through an enclosure, but their effect is difficult to regulate. The sensitivity of optical fibers and connectors to excessive force dictates that a force-guided manipulation should be well controlled to minimize fiber and connector damage. It is preferable to abandon a particular routing pathway that causes too much bending or friction, than to apply inordinate pulling force to the optical fibers and connectors. 
     The difficulties in applying appropriate pulling forces to connectorized optical fibers may be overcome by placing a “breakaway” component or intermediate force-sensitive device along the pulling pathway. This device would disengage the optical fiber from the pulling force at a predetermined pulling resistance, thereby protecting the optical fiber and its connector from damage and deterioration. The device of the present invention inserts a breakaway component along the path between the optical fiber being pulled and its pulling force. The breakaway device prevents damage to the optical fiber and connector by breaking at a predetermined tension, thereby allowing the user to reconfigure the routing to prevent damage to the fiber. 
     SUMMARY OF THE INVENTION 
     The device of the present invention operates by disconnecting a pulling force from a connectorized optical fiber at a predetermined tension. By separating an excessive pulling force from a connectorized optical fiber, both the fiber and the connector are protected from damage and remain functional. A force-sensitive breakaway component may be inserted along the pathway connecting a pulling force to at least one optical fiber, or the pulling line itself may have breakaway capabilities. A breakaway cap may also be placed over the front end of the optical fiber, such that a portion of the breakaway cap releases the pulling cord upon excessive pulling force. 
     It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention, and together with the description serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a breakaway component in an open configuration with a connectorized optical fiber according to a first embodiment of the present invention; 
     FIG. 2 is a top view thereof; 
     FIG. 3 is an isometric view of the breakaway component of FIG. 1 in a closed position with a pulling cord attached; 
     FIG. 4 is an isometric view of a breakaway component in a closed position with a pulling cord attached according to a second embodiment of the invention; 
     FIG. 5 is a top view of a breakaway component according to another embodiment of the invention; and 
     FIG. 6 is a top view of a breakaway component according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention relates to breakaway devices for disconnecting the terminal end of a connectorized optical fiber from a pulling force. The breakaway device may be placed at different locations along the connection between the pulling force and the connector covering the optical fiber, depending upon the particular demands of the environment in which optical fibers are being routed or the characteristics of the optical fibers and connectors themselves. For situations in which it is preferable to disconnect the connector covering the optical fiber from the pulling force by breaking apart a portion of a clamshell cover, the first embodiment of the present invention is presented. Another embodiment of the invention has a breakaway piece on a connector cover that breaks when excess tension is applied. Another embodiment of the present invention utilizes a breakaway component in a device that is along the line connecting the front end of the connectorized optical fiber and the pulling force. 
     Referring to the first embodiment in FIG. 1, a breakaway cap  10  is shown holding a connector  12  mounted on an end of an optical fiber  14 , employing standard mounting techniques, including strain relief using, for example, a crimp body and crimp ring to hold strength members (e.g., Kevlar® fibers) associated with the optical fiber. The breakaway cap  10  is preferably of a elongated clamshell design, in which a first segment  18  and a second segment  20  are connected by a hinge element  28 , but any shape would be possible. The cap  10  is shown in FIG.  1  and FIG. 2 in an open configuration. An optical fiber  14 , which is shown as ribbon cable, but could be of any type or configuration, has a connector  12  mounted on a first end  16  of the optical fiber  14  and is held in recess  22  defined by the inner surface  24  of the breakaway cap  10 . The holding recess  22  preferably has a shape that closely corresponds to the connector  12 , and preferably engages the connector  12  at the second end  26  of the recess  22  where is it is narrower than at the first end  30 , preventing the connector from pulling out of the cap  10 . 
     When the connector  12  mounted on the optical fiber  14  is placed into the holding recess  22 , the first and second segments  18 ,  20  of the cap  10  cooperate to enclose the connector  12 . The connector  12  and the front end  16  of the optical fiber  14  are securely held by the closed breakaway cap  10  and resist dislocation toward the second end  26  of the cap  10  due to the narrowing of the holding recess  22  at the second end  26  and larger width of the connector  12 . While cap  10  does not have any elements to secure it in the closed position (see FIG.  3 ), cap  10  may have such securing elements if so desired. However, the shape of recess  22  closely corresponds to the connector  12  and connector  12  may aid in keeping the cap  10  closed during operation. Additionally, as shown in FIG. 3, the first and second segments  18 , 20  are held together by the pulling cord  38 , as described below. 
     A breakaway pulling loop  34  forms an opening at the first end  30  of the breakaway cap  10 . A force-sensitive tongue  32 , contiguous with the material of the breakaway cap  10 , extends from its first end  30  to circumscribe the outermost perimeter of the pulling loop  34 . The material of the breakaway cap  10  and that of the force-sensitive tongue  32  of the pulling loop  34  are of a thickness and conformation that support up to a specified pulling force, so that the force-sensitive tongue  32  breaks apart releasing the pulling cord  38  when that force is exceeded. The force required to break through the tongue  32  depends on the specific connector and the strength members associated with the optical fiber. For larger connectors and larger numbers of optical fibers, the strength of the connection between the connector and the optical fibers/cable increases. Therefore, the larger the connector/number of fibers, the larger the force the connectorized optical fiber can withstand and the thicker the tongue  32  could be. 
     As best seen in FIGS. 2 and 3, the force-sensitive tongue  32  may have a notch  37  or have some other geometric design to facilitate the breakaway at a predetermined force. The pulling loop  34  is preferably shaped to facilitate placement of the pulling cord in the opening  36 , so that the tension is applied at the tongue  32  to ensure proper operation. 
     As illustrated in FIG. 3, the pulling cord  38  may be passed through the pulling loop  34  of a closed breakaway cap  10  enclosing at least one connector  12  covering an optical fiber  14  and also be connected to a pulling device (not shown). The pulling cord  38  may be tied at the cap  10  to assist in keeping the cap  10  in a closed position during use. Alternatively, the cord  38  could be secured anywhere between the cap  10  and the pulling device. The force applied by the pulling device and transferred to the pulling cord  38  would draw the breakaway cap  10 , the connector  12 , and optical fiber  14  along the pathway routed by the cord  38 . If force were applied in excess of that permitted by the configuration of the breakaway cap  10 , the force-sensitive tongue  32  would break apart, thereby releasing the pulling cord  38  that had been fastened to pull the optical fiber  14 . A connectorized optical fiber  14  housed within the breakaway cap  10  could then be drawn back to its original location, and another attempt (using another cap  10 ) to position the optical fiber  14  could commence. Advantages of the breakaway cap  10  include its protective capabilities in covering the front end of the optical fiber  14  and connector  12 , as well as its ease in replacement once the optical fiber has been drawn back to its starting position for re-routing. As the breakaway cap is a single element, no assembly of multiple parts is required. 
     An alternative to connecting the pulling cord to a pulling loop on the breakaway cap would be to mount a breakaway knob on the outer surface of a breakaway cap. As shown in the embodiment in FIG. 4, a closed breakaway cap  50  having a breakaway knob  52  on its front end  54  may be used to secure a pulling cord  58  to a connectorized optical fiber  56 . The knob  52  is connected to the cap  50  by a piece  53 , which may also have a notch as in the first embodiment, having a reduced diameter relative to the cap  10 . The reduced diameter piece  53  is designed to break at a predetermined force. As in the first embodiment, the breaking force is dependent on the connector and the strength members associated with the optical fiber. 
     Another embodiment of the present invention positions a breakaway element along the path of the pulling cord connecting a connectorized optical fiber and a pulling force. Referring to FIG. 5, a breakaway element  100  is shown that has a rounded body  102 , with a first pole  104  and second pole  106 . While a round body is shown, any shape or dimension is acceptable, although bodies that are smaller and with no sharp edges to catch are preferable. Each pole ( 104 ,  106 ) has a force-sensitive portion  108  defining a pulling opening  110 . Pulling cords may be secured through each opening  110  at each pole ( 104 ,  106 ), and one of the poles would then connect with a connectorized optical fiber and the other pole with a pulling force. 
     As an alternative to a pulling opening  110  covered by a force-sensitive portion  108  that breaks upon reaching excessive pulling force, the element  100  may also comprise a body  102  that employ breakaway knobs, as shown above in FIG. 4 or a combination of the openings  110  and the knobs. Furthermore, only one pole of the element  100  may have a breakaway portion  108  while the other pole may firmly retain its pulling cord. 
     Another embodiment is shown in FIG.  6 . In this embodiment, the breakaway mechanism is similar to that shown in FIG. 5, but may also include of the body  122  of the element  100 , rather than the pulling openings  130  at the first pole  132  or second pole  134 . As shown in FIG. 6, a divider groove  124  traverses the circumference of the body  122 , weakening the structure of the breakaway element  120  such that the element  120  breaks apart into a first segment  126  and a second segment  128 , or even multiple smaller segments, upon reaching an excessive pulling force. 
     The breakaway cap (FIGS. 1-4) or breakaway element (FIGS. 5 and 6) could be fabricated from virtually any material ranging from metals to plastics, as long as the article breaking apart (e.g., the force-sensitive tongue, knob, or element) were of a strength that would permit appropriate pulling of optical fibers, but would break apart upon reaching a force limitation. The first embodiment having a clamshell design could be preferably made from molded plastic, facilitating installation and allowing for disposability. 
     Although the present invention has been described with respect to certain preferred and alternative embodiments, it should be understood that various changes, substitutions and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, substitutions, and modifications as fall within the scope of the appended claims and their equivalents.