Abstract:
A separation and regrouping device for conductive elements such as optical fibers is disclosed. The device includes a housing and a plurality of conductive elements extending through an interior region thereof. The housing surrounds encapsulation discontinuities formed on the conductive elements. The housing can include a guide channel that channels the optical fibers through the interior region thereof and, optionally, rotates the fibers as they extend through the housing. The device can also include strain relief elements that contain the optical fibers and surround the encapsulation discontinuities, and potting chambers in which the optical fibers can be potted to the housing. Methods for organizing conductive elements are also disclosed that include providing a plurality of conductive elements arranged in first groups, separating the first groups into individual conductive elements, and rearranging the individual conductive elements into second groups.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The subject matter disclosed herein is related to the subject matter disclosed in copending application Ser. No. 09/639,267, filed on even date herewith, entitled “Shuffle Device,” the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to a shuffle device, and more particularly, to an optical fiber separation and regrouping device for an optical shuffle. 
     BACKGROUND OF THE INVENTION 
     Optical fibers provide a well-known medium for conveying information in data and communications systems, such as computer and telephone systems. It is well known, that optical fibers possess characteristics wherein their light transmission capability is greatest when the fiber is straight and devoid of bends, and that they are subject to signal attenuation due to bending. These bending losses can be characterized as losses due to larger, gradual bends (macrobends), and losses due to much smaller and sharper bends (microbends). Macrobends can result from winding the fiber, for example, while microbends arise because of random variations in direction of the core axis. 
     Optical fibers, therefore, are typically provided with protective coatings to preserve the inherent strength of the glass and to buffer the fiber from microbending induced attenuation. Individual optical fibers can be encapsulated in a polymer casing that protects the fiber from damage, or an optical fiber ribbon can be formed by aligning a plurality of optical fibers in a linear array and then encapsulating the fiber array in a polymer casing to form the ribbon. 
     Two coatings are generally used to form a fiber optic cable or ribbon. The first coating, which is typically applied to the surface of the optical fiber, is generally referred to as the primary coating. The primary coating, once cured, is a soft, rubbery material that serves as a buffer to protect the fiber by relieving the stress created when the fiber is bent. The primary coating usually has a low glass transition temperature to provide resistance to microbending. 
     Certain characteristics are desirable for the primary coating. For example, the primary coating must maintain adequate adhesion to the glass fiber during thermal and hydrolytic aging, yet be strippable for splicing purposes. The modulus of the primary coating must be low to cushion and to protect the fiber by relieving stress on the fiber, which can induce microbending and, consequently, inefficient signal transmission. It is desirable for the primary coating to have a low glass transition temperature to ensure that the coating remains in a rubbery state throughout a broad temperature range. 
     The secondary or outer coating is applied over the primary coating. The secondary coating functions as a hard, protective layer that prevents damage to the glass fiber during processing and use by providing desired resistance to handling forces, such as those encountered when the coated fiber is cabled. 
     Additionally, it is often desirable to switch information between systems that use optical fibers as information conveyance media. This can be accomplished by directing the optical fibers output from each system into one or more systems. This is known as shuffling the fibers, and the mechanism by which this is accomplished is known as an optical shuffle. An optical shuffle in which one fiber output from each system is directed to a different system is known as a perfect shuffle. Thus, in a perfect shuffle, each system can communicate with every other system. 
     One way by which an optical shuffle can be formed is to strip the coatings from the fibers or ribbons inputted to the shuffle, and then “re-ribbonize” the exiting fibers. That is, the stripped fibers can be grouped differently, re-encapsulated, and then output from the shuffle. Thus, a discontinuity is created in the area of re-ribbonization, and the fibers can remain undesirably exposed in that region. Moreover, the fibers are prone to strain and bending in the area of the discontinuity. 
     There is a need in the art for a compact optical shuffle that permits re-ribbonization of a plurality of optical fibers, while protecting the fibers from damage and reducing strain and bending in the discontinuity. It is an objective of the present invention, therefore, to provide an optical fiber separation and regrouping device that protects and controls bending of the optical fibers at the discontinuity. 
     SUMMARY OF THE INVENTION 
     The present invention is a separation and regrouping device comprising a housing and a plurality of conductive elements, such as optical fibers, extending through an interior region of the housing. The optical fibers can be encapsulated individually as fiber optic cables, or grouped together and then encapsulated to form optical fiber ribbons. 
     Each optical fiber has a first coating disposed along a first portion thereof, and a second coating disposed along a second portion thereof. An encapsulation discontinuity is formed on each optical fiber between the first coating and the second coating. The housing can be pre-assembled or molded over the optical fibers to contain the optical fibers and surround the encapsulation discontinuities. 
     The interior region of the housing can include a guide channel that channels the optical fibers through the interior region of the housing. The guide channel can be a single channel, or can include a plurality of channels. The guide channel can also be twisted to rotate the fibers as they extend through the housing. 
     The device can also include one or more strain relief elements within the interior region of the housing that contain the optical fibers and surround the encapsulation discontinuities. A single strain relief element can contain a plurality of fibers, or the device can include a plurality of strain relief elements, each of which contains a single fiber. 
     To further reduce strain on the conductive elements, the housing can also include one or more potting chambers in which the optical fibers can be potted to the housing. 
     A method according to the invention for organizing conductive elements includes providing a plurality of conductive elements arranged in first groups, separating the first groups into individual conductive elements, and rearranging the individual conductive elements into second groups. 
     The first groups can be optical fiber ribbons, which are separated by unribbonizing the fibers (e.g., by stripping the encapsulation from the ribbon to expose the fibers). The unribbonized fibers can then be re-ribbonized (i.e., rearranged into a second group and encapsulated to form a second ribbon). 
     Thus, a method according to the invention for managing a plurality of conductive elements includes arranging a first section of the conductive elements in a first arrangement, arranging a second section of the conductive elements in a second arrangement, and enclosing a third section of the conductive elements located between the first and second sections. 
     The third section of the elements can be enclosed by inserting the conductive elements in a pre-assembled shuffle device, or by encapsulating the conductive elements such as by overmolding a housing over the third section, or by potting the third section within a tubular structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described in the accompanying drawings in which: 
     FIG. 1 is a longitudinal cross section of a preferred embodiment of a separation and regrouping device according to the present invention; 
     FIG. 1A provides an enlarged view of an input end of a separation and regrouping device according to the invention; 
     FIG. 1B provides an enlarged view of an output end of a separation and regrouping device according to the invention; 
     FIG. 2 is a cross sectional view of an exemplary input fiber matrix; 
     FIGS. 3A and 3B are cross sectional views of an unrotated output fiber matrix before and after re-ribbonization; 
     FIG. 4 is a longitudinal cross section of an alternative embodiment of a separation and regrouping device according to the present invention; 
     FIG. 5 is a longitudinal cross section of still another preferred embodiment of a separation and regrouping device according to the present invention; and 
     FIGS. 6A and 6B are cross sectional views of a rotated output fiber matrix before and after re-ribbonization. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As shown in FIG. 1, a separation and regrouping (i.e., “shuffle”) device  100  for conductive elements such as optical fibers comprises a housing  102 , and a plurality of optical fibers  110 . Housing  102  has an input end  102 A, an interior region  104 , and an output end  102 B through which optical fibers  110  extend. 
     Each optical fiber  110  is coated with a respective first coating  110 ′ disposed along a first, or input, portion  110 A thereof. An individual optical fiber  110  can be coated along its input portion  110 A to form an input cable  112 , or a set of optical fibers  110  can be arrayed and coated together along their respective input portions to form an input ribbon  114 . Device  100  can include any number of input cables  112  or input ribbons  114 , or any combination of input cables  112  and input ribbons  114 . 
     In a preferred embodiment, the set of input cables  112  and input ribbons  114  can be configured as an input fiber matrix  116  as shown in cross section in FIG.  2 . As shown, input matrix  116  can include three input ribbons  114   a-c , each having six optical fibers  110   a-c , respectively, although input matrix  116  can comprise any number or combination of input ribbons  114  or input cables  112 , and, in general, an input ribbon  114  can include any number of fibers from 1 to N. Thus, for purposes of this specification, an input cable  112  can be said to be an input ribbon  114  having only one optical fiber  110 . Note that input matrix  116  is oriented so that the ribbons  114  are parallel to the direction indicated by arrow C. 
     The following describes a pre-assembled housing  102 , which could be made from plastic or metal. With reference once again to FIG. 1, housing  102  is shown to include an input aperture  120  that receives the entire input fiber matrix  116 . In a preferred embodiment of the present invention, input end  102 A of housing  102  is adapted to receive an input fiber matrix  116  having twelve ribbons of twelve fibers each, although, in general, device  100  can be adapted to receive N ribbons having M(n) fibers each, where 1&lt;=n&lt;=N, and M(n) is the number of fibers included in ribbon n, with M(n)&gt;=1. 
     To reduce the incidence of bending, housing  102  can include a guide channel  142  that guides fibers  110  through interior region  104  of housing  102 . Preferably, guide channel  142  includes a plurality of channels  144  that extend through housing  102 . Each channel  144  is sized and shaped to accommodate either a discrete cable  112  or a ribbon  114  of fibers. 
     Each optical fiber  110  is coated with a respective second coating  110 ″ disposed along a second, or output, portion  110 B thereof. An individual optical fiber  110  can be coated along its output portion  110 B to form an output cable  122 , or a set of optical fibers  110  can be arrayed and coated together along their respective output portions to form an output ribbon  124 . Device  100  can include any number of output cables  122  or output ribbons  124 , or any combination of output cables  122  and output ribbons  124 , although the total number of optical fibers  110  that extend through output end  102 B of housing  102  should equal the number of optical fibers  110  that extend through input end  102 A of housing  102 . That is, optical fibers are neither created nor destroyed within device  100 , they are merely separated (if they are part of an input ribbon) and regrouped (to form an output ribbon) as will be described below. Thus, in general, device  100  can be used to transform N ribbons having M(n) fibers, into X ribbons having Y(x) fibers, where 1&lt;=x&lt;=X, and Y(x) is the number of fibers included in ribbon x, with Y(x)&gt;=1. 
     Although any or all of the input ribbons can extend through housing  102  and emerge from output end  102 B in the same configuration (i.e., the same fibers are grouped together on output as on input), device  100  can be used to separate the array of fibers that form an input ribbon  114 , and then regroup and re-ribbonize a second array of fibers, on the output side of the device, to form an output ribbon  124 . FIGS. 3A and 3B provide cross sectional views of an unrotated output fiber matrix  118  before and after re-ribbonization. Note that, in FIG. 3A, output matrix  118  is oriented so that output ribbons  124  are parallel to the direction indicated by arrow C, while in FIG. 3B, re-ribbonized output matrix  118 ′ is oriented so that output ribbons  124 ′ are perpendicular to the direction indicated by arrow C. 
     Output matrix  118  can be re-ribbonized in any manner known to those in the art, although it is preferred that the encapsulation is removed from a distal portion of each ribbon by peeling, or through the use of chemicals or heat strippers, or by any other suitable technique known in the art, to expose optical fibers  110 . The exposed fibers are preferably encapsulated to form a plurality of output ribbons  124   a-f . The ribbons, in combination, form within chamber  140 B, an output ribbon matrix  118 ′. Preferably, each output ribbon  124   a-f  includes one fiber  110  from each input ribbon  114   a-c.    
     Thus, it is the process of re-ribbonizing the output fiber matrix that causes the optical fibers  110  to have a first coating  110 ′ disposed along first portion  110 A thereof and a second coating  110 ″ disposed along second portion  110 B thereof. As shown in FIG. 1, a respective encapsulation discontinuity  130  is formed on each optical fiber  110  where optical fiber  110  has no coating (i.e., the between its first, or input, coating  110 ′, and its second, or output, coating  110 ″). Preferably, all the respective encapsulation discontinuities  130  are formed in the same general area, or region  132 , within housing  102 . 
     FIGS. 1A and 1B provide enlarged views of the input and output ends of the device, respectively, thereby better showing the detail of the encapsulation discontinuities  130 . 
     To further reduce the incidence of bending, fiber separation and regrouping device  100  can also include one or more optional strain relief elements. Device  100  can include a single strain relief element  134  that surrounds all the fibers  110  in region  132  at the output end of housing  102 . Preferably, strain relief element  134  is a small, plastic tube that contains a plurality of fibers (preferably, all of them) to keep them from bending in region  132 . Alternatively, or additionally, device  100  can include one or more individual strain relief elements  136  that surround the respective discontinuities  130  of individual optical fibers  110  or where the ribbons  114  have been separated into discrete cables  112  at the input end of housing  102 . Preferably, each strain relief element  136  is a small, plastic tube that contains an individual optical fiber  110  to keep it from bending at its encapsulation discontinuity  130 . 
     To still further reduce bending, the input and output fiber matrixes can be potted (e.g., epoxied) to housing  102 . To accomplish this, housing  102  can include an input potting chamber  140 A for potting input cables  112  and input ribbons  114 . Similarly, housing  102  can include an output potting chamber  140 B for potting output cables and ribbons. The potting chambers  140 A,  140 B can be filled with epoxy or other such potting material to hold the fibers in place. This stabilizes the fibers (and strain relief elements  134 ,  136 , if present) and thereby reduces strain. Thus, device  100  can serve to enclose the fibers, without the need for any additional housing. As shown in FIG. 3B, output ribbons  124 ′ are oriented in the same direction as input ribbons  112   a-c  (see FIG.  2 ). Although it, it should be understood that, in general, output ribbons  124 ′ can be oriented in any direction relative to input ribbons  112 , it is preferred, for routing purposes, that output ribbons  124 ′ are in the same orientation as input ribbons  112 , that is, generally parallel to the direction of arrow C. To accomplish this, a device according to the present invention can be used to rotate the ribbon matrix as it extends though the housing so that, after re-ribbonization, the output ribbons are oriented in the same direction as the input ribbons. 
     Device  100  can also include one or more mounting members  146  that extend from housing  102 . Mounting members  146  can be used to mount device  100  to one or more substrates, such as printed circuit boards (PCBs). 
     It is known that the optical fibers are prone to both macrobending and microbending at their respective encapsulation discontinuities  130 . In an alternative embodiment to the pre-assembled housing, housing  102  could be molded over the optical fibers at region  132  to contain the fibers and reduce the incidence of bending in region  132 . In this embodiment, housing  102  can be made of a polymer, such as plastic, and is molded over the optical fibers. 
     In another embodiment, shown in FIG. 4, housing  102 ′ could be a generally tubular structure with open ends and an open interior. Once the fibers  110  are passed therethrough, housing  102 ′ could then be potted with known materials, such as epoxy. The epoxy fills the remainder of the open interior of the housing not occupied by the fibers. The epoxy retains the fibers in position and provides strain relief. 
     FIG. 5 shows a cross-section of a shuffle device  200  for separating and regrouping optical fibers that includes twisted guide channels  144 . Device  200  is similar to device  100 , except that channels  144  are twisted. As the input fiber matrix extends through housing  102 , the fiber matrix is rotated from a first orientation at input end  102 A (as shown in FIG. 2) into a second orientation at output end  102 B (as shown in FIG. 6A) because of the twists. Output fiber matrix  118  can now be “re-ribbonized,” as described above, to form a rotated re-ribbonized output fiber matrix  118 ″, a cross sectional view of which is depicted in FIG.  6 B. Note that output ribbons  124 ″  a-f  are once again parallel to the direction given by arrow C. 
     Although the output fiber matrix can, in general, have any orientation relative to the orientation of the input fiber matrix, (i.e., guide channel  144  can be twisted to rotate the fiber matrix any number of degrees), it is preferred that guide channel  144  is twisted to rotate the fiber matrix approximately 90 degrees so that the output ribbons after re-ribbonization can be made parallel to the input ribbons. This helps to reduce the overall size of the device. 
     A fiber device according to the present invention can be sized for any application, although it is usually desirable that the device be as small as possible, especially for applications where available space is limited. For example, in a preferred embodiment, device  100  can be about 50 mm long and have a cross section of about 10 mm×10 mm. 
     While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.