Abstract:
A reel for storing optical fiber is disclosed that significantly reduces the torsional force applied to optical fiber as the fiber is being wound onto the reel for storage. The optical fiber reel comprises two spindles that are offset with respect to the rotational center of the reel. Such an arrangement causes the fiber to be wound onto the reel in a substantially linear fashion, thus preventing the torsional force and resulting twisting that cause micro-cracks to develop. The spindles are of a sufficiently large diameter to facilitate operational use of the fiber while stored on the spindle without increasing the attenuation of signals that could result from the use of a smaller diameter spindle.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to optical fiber and, more particularly, to the storage of optical fiber. 
   BACKGROUND OF THE INVENTION 
   The use of optical fiber has become widespread in telecommunications applications. Light signals passed along such fiber are capable of extremely high data throughput rates, especially when coupled with throughput optimizing technologies such as dense wavelength division multiplexing (DWDM). Higher throughput over an optical fiber, as is used in long-distance optical transmissions, typically requires a signal with higher power and, accordingly, the fiber must be designed to increasingly stringent design tolerances to accommodate that higher power. 
   In telecommunications facilities, such as switching facilities, it is often necessary to connect multiple components with lengths of optical fiber. Traditionally, it has been desirable to use the minimum length of fiber necessary to connect the components to avoid clutter in the facilities. As a result, a typical method of connecting two components has been to measure the length of optical fiber necessary to connect two components and use a length of fiber having connectors on each end to connect to the respective components. If the components were then moved with respect to each other, reconnecting them was simply a matter of obtaining a longer length of fiber and attaching connectors to that new fiber. 
   However, while using such connectors with optical fibers is sufficient in relatively low-power optical applications, it becomes less desirable as the power of the optical signal passed across the fiber increases, such as the case in long-haul optical transmission applications. This is because optical fiber carrying relatively high power signals tends to fail more readily at the connector due to, for example, signal leakage and heat build-up at the connector. Therefore, in more recent attempts at connecting two or more optical components, multiple lengths of fiber were spliced together to avoid the need for connectors. Splicing for high-power applications requires very stringent alignment of the fibers to prevent discontinuities in the spliced fiber. Thus, the splicing operation was often a time consuming effort. Therefore, in order to eliminate the need for re-splicing the fiber in the event the components were moved relative to one another, a long length of fiber was used. The resulting spliced length of optical fiber between the two components typically significantly exceeded the minimum length necessary to connect those components. In order to prevent clutter due to the excess fiber, spools were used to store the excess fiber. Thus, for example, if the components were relocated subsequent to being connected, additional fiber was available to bridge any increased separation distance between the components. 
     FIGS. 1A and 1B  show, respectively, a three dimensional view and a top view of an illustrative prior spool  101  used for storing such excess fiber. In those figures, fiber  102  was wound around a central spindle  103  that was supported by side members  106 . One end of optical fiber  102  extended in direction  105  and was connected to a first optical component and a second end of optical fiber  102  extended in direction  104  and was connected to, illustratively, a second optical component. When additional fiber was needed, e.g., to bridge the aforementioned increased separation distance due to moving the components, the fiber could simply be unwound from the spool. Thus, the costs associated with repeated splicing of fiber in relatively high power applications were avoided. 
   SUMMARY OF THE INVENTION 
   While prior attempts at storing excess fiber between optical components, such as the aforementioned spools, were advantageous in many applications, they were limited in certain regards. For example, although prior storage spools prevented clutter and eliminated the need for multiple splicing operations in the case where components were moved, the present inventors have recognized that storing fiber on such spools introduced a torsional force to the fiber. This force tended to cause the fiber to twist as it was being wound onto the spools. Over time, the stress resulting from this torsional force/twisting caused small cracks, known as micro-cracks, to develop in the optical fiber. Such micro-cracks tend to increase attenuation of an optical signal when a relatively low power is passed over fiber with such cracks. However, the problem is much more significant when high-power signals are transmitted over fiber such that, when micro-cracks are present in the fiber, the fiber may actually heat at the location(s) of the micro-cracks to the point of melting. 
   Therefore, the present inventors have invented a reel for storing optical fiber that significantly reduces the torsional force applied to the fiber as it is being wound onto the reel for storage. Specifically, the present inventors have invented an optical fiber reel that utilizes two spindles that are offset with respect to the rotational center of the reel. Such an arrangement causes the fiber to be wound onto the reel in a substantially linear fashion, thus preventing the torsional force and resulting twisting that cause micro-cracks to develop. Additionally, the spindles are of a sufficiently large diameter to facilitate operational use of the fiber while stored on the spindle without increasing the attenuation of signals that could result from the use of a smaller diameter spindle. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIGS. 1A and 1B  shows, respectively, a three dimensional view and a top view of an illustrative prior art spool used to store optical fiber in a telecommunications facility; 
       FIGS. 2A and 2B  show a top view and a side view, respectively, of an optical fiber reel in accordance with the principles of the present invention; 
       FIG. 3  shows the optical fiber reel of  FIG. 2A  wherein a fiber is secured to the reel; 
       FIGS. 4A and 4B  show a top view and a side view, respectively, of how fiber is wound onto the optical fiber reel of  FIGS. 2A and 2B ; 
       FIGS. 5A and 5B  show a three dimensional view and a side view, respectively, of how two or more fiber reels in accordance with the principles of the present invention can be used together; 
       FIGS. 6A and 6B  show a three-dimensional view of an illustrative holder for the fiber reels of  FIGS. 5A and 5B ; and 
       FIGS. 7A and 7B  show a three-dimensional view and a side view of how a housing can be used to enclose the fiber reels of  FIGS. 5A and 5B  within the holder of  FIGS. 6A and 6B . 
   

   DETAILED DESCRIPTION 
     FIGS. 2A and 2B  show a top and a side view, respectively, of an optical fiber reel  201  in accordance with the principles of the present invention. As compared to prior fiber spools, such as that illustrated in  FIGS. 1A and 1B , the illustrative reel of  FIGS. 2A and 2B  is characterized by a support member  207  upon which two optical fiber spindles  202  are mounted. Reel  201  is illustratively manufactured from an aluminum or plastic material, although other materials would be equally advantageous. Spindles  202  have a radius that is sufficient to prevent excessive bending of the optical fiber, exemplarily a radius of ½ of an inch, so that, at relatively high signal powers (e.g., 1 Watt), the signal transmitted over the fiber will not be significantly attenuated. For illustrative purposes, support member  207  is herein shown as a circular disk. One skilled in the art will recognize that many different disk materials, shapes and configurations will be equally advantageous. Illustratively, the two spindles  202  are offset from the rotational center  206  of the reel. As described further below, spindles  202  are useful for storing optical fiber that is operational, i.e., that is in operational use for the transmission of optical signals. One skilled in the art will also recognize that, while two spindles are illustrated in the figures herein, three or more spindles may be used equally advantageously in accordance with the principles of the present invention. The fiber reel of  FIGS. 2A and 2B  has, illustratively, holes  208  that are adapted to hold a clip that may be used to hold down a portion of the optical fiber, such as for example a region of spliced fiber, to facilitate the winding of the fiber onto the reel  201 . Holes  203  may be used, for example, as finger holes to facilitate manual winding of the fiber onto the reel. Holes  205  are, illustratively, holes adapted to receive screws for mounting spindles  202  onto disk  207 . Finally, holes  204  described further herein below, are adapted to receive screws that may be used to hold reel  201  stationary relative to a holding apparatus once the fiber has been wound onto reel  201 . 
     FIG. 3  shows reel  201  of  FIG. 2A  holding a length of fiber  302  that is, illustratively, a fiber connecting two optical components. Fiber  302  is clipped to disk  201  illustratively, by clip  301  that is adapted to be secured to disk  201  via holes  208  in  FIG. 2 . The portion of fiber  302  under clip  301  is, for example, that point on the fiber that is half the distance along that fiber from illustrative optical components connected to both ends of fiber  302  and may be, illustratively, that portion of fiber where two fibers are spliced together. Thus situated, the secured portion of the fiber will be held securely by clip  301  thus minimizing any stress experienced by that portion of fiber. To begin winding the fiber onto reel  201  holes  203  can illustratively be used to manually rotate disk  207  in direction  303 , thus causing the fiber to be wound around spindles  202 . One skilled in the art will recognize that many methods of winding fiber onto the reels will be equally advantageous such as, for example, other manual or mechanical means. 
     FIGS. 4A and 4B  show the illustrative fiber reel  201  of  FIGs. 2A and 2B  wherein fiber is wound around the spindles  202  on disk  207 . As described above, holes  203  are illustratively used to rotate disk  207  in direction  303 . Thus, for example, fiber  302  enters the reel  201  from directions  401 A and  401 B from two separate optical components. As reel  201  is turned in direction  303 , the fiber is wrapped around spindles  202  in direction  402  until a desired amount of the excess fiber is wound around spindles  202 . This manner of winding fiber onto reel  201 , with the fiber secured under clip  301  and wound around spindles  202 , ensures that the fiber  302  is linearly wound around the spindles  202  such that substantially no torsional force is applied to the fiber as it is wound. Thus, unlike with prior fiber spools, the fiber does not twist and, accordingly, no stress-induced micro-cracks occur during storage. 
     FIG. 5A  shows a three-dimensional view of two fiber reels  501  and  502  of the type illustrated in  FIGS. 4A and 4B .  FIG. 5B  shows the two fiber reels of  FIG. 5A  as viewed from direction  507 . Collectively,  FIGS. 5A and 5B  show illustrative reels  501  and  502  that are configured to be placed on top of one another to facilitate more compact storage of the reels once the fibers  504  and  505  are wound onto the spindles  508 . Illustrative holes  506 , as well as finger holes  508 , allow air to pass through reels  501  and  502 . 
     FIGS. 6A and 6B  show a three-dimensional view and a top view of an illustrative holding member  603  used to store the reels of  FIGS. 5A and 5B . Specifically, plate  605 , which is illustratively manufactured of aluminum, has support members  601  spaced apart from their opposing members on plate  605  a distance slightly more than the diameter of reels  501  and  502 . Thus situated, reels  501  and  502  will be laterally held in place by posts  601  and plate  605  (I.e., the reels will be limited in their movement in directions  607 ) while, at the same time, it will still be possible to rotate the reels to adjust the amount of fiber  504  and/or  505  stored on reels  501  and  502 , respectively. Referring to  FIG. 6B , illustrative holes  604  are disposed vertically in posts  601 . These holes are, for example, adapted to hold screws such that the upper portion (e.g., the head) of the screw overlaps the reel  501  and secures that real in place, thereby preventing any rotation of the reels. Each of the holes  604  in each of the posts  601  is located at a height relative to the reels such that, upon inserting screws into each of the holes, a different reel will be secured. Thus, for example, screw  602  is located at a height such that it can secure reel  501 . Similarly, screw  606  is located at a height such that it can secure reel  502 . The third hole in the posts  601  is, illustratively, adapted to hold a screw for securing a third reel not shown in  FIGS. 6A and 6B . 
   The present inventors have recognized that the illustrative holder of  FIGS. 6A and 6B  may serve other purposes other than acting as a holder for reels  501  and  502 . For example, if holder  603  is manufactured from heat-conductive material (such as the aforementioned aluminum), the bottom of the holding member may be adapted to be attached to a heat-generating component, such as a computer processor. Thus attached, holding member  603  could also serve as a heat-dissipation device (i.e., a heat sink) for dissipating the heat generated by that component. In such a use, holes  506  and holes  503  become especially useful in allowing air to pass through the reels  501  and  502  in order to facilitate such heat dissipation. 
     FIGS. 7A and 7B  show an additional embodiment in accordance with the principles of the present invention. Specifically,  FIGS. 7A and 7B  show a three-dimensional view and a side view, respectively, of the fiber reels  501  and  502  and holding member  603  of  FIGS. 6A and 6B  wherein a cover plate  701  is used to remove a fiber reel after it has been placed in the holding member. It may be necessary to remove a fiber reel, for example, to gain access to underlying fiber reels. Also, in the case where the holding member  603  of  FIGS. 6A and 6B  acts as a heat sink for electronic components, it may be necessary to remove the fiber reels from the holding member in order to facilitate access to the underlying electronics components. In order to remove a fiber reel, screws  702  are illustratively screwed into holes  703  on reel  501  to attach cover plate  701  to that reel. Cover plate  701  can then be lifted away with fiber reel  501  attached, thus providing access to the reels or electronic components underneath reel  501 . Flanges  705  fit closely to the support member  207  of reel  501 , thus helping to secure the fiber  504  when reel  501  is lifted out of holding member  603 . 
   The foregoing merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are within its spirit and scope. For example, one skilled in the art, in light of the descriptions of the various embodiments herein, will recognize that the principles of the present invention may be utilized in widely disparate fields and applications. All examples and conditional language recited herein are intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting aspects and embodiments of the invention, as well as specific examples thereof, are intended to encompass functional equivalents thereof.