Abstract:
A system and method for the vacuum assisted insertion of optical fibers includes a plate with one or more fiber alignment holes and a vacuum-sealed region on the exit end of the alignment holes. A vacuum source is connected to the vacuum-sealed region and creates a partial vacuum which draws air through the alignment holes creating an airstream into the alignment hole. As a fiber is moved toward the alignment hole, the airstream converging on the hole creates a centering force which acts to pull the fiber into alignment with the hole and the fiber passes directly into the hole. The use of a vacuum produces a precise alignment of a fiber or fibers that can be automated and is significantly quicker and more efficient than any other existing apparatus.

Description:
RELATED APPLICATION 
     This application is a continuation in part of Provisional Patent Application Ser. No: 60/273,437 entitled “Vacuum Assisted Insertion of Optical Fibers” filed Mar. 5, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to optical fibers. More specifically, the present invention pertains to methods of positioning and aligning optical fibers within a fiber optic system. The present invention is particularly, though not exclusively, useful for quickly and accurately inserting optical fibers into fiber ferrules and other fiber alignment devices. 
     BACKGROUND OF THE INVENTION 
     Over the past several decades, the use of optical fibers, or fiber optics, to transmit information on a light beam have become increasingly popular. In fact, much of the information which is transmitted today within the telecommunications industry is done over optical fibers. 
     A typical single mode (SM) optical fiber has a diameter of approximately 125 microns (125 μm) and is formed with a glass core with a diameter of about ten microns (10 μm). As a result, these optical fibers are rather flexible, yet must be positioned to a very high degree of precision. 
     As a result of the widespread use of optical fibers, and the fact that the typical optical fibers are very small and flexible, the handling, positioning and termination of these fibers represents a significant challenge to manufacturers of high quality fiber-optic products. Moreover, because some optical equipment incorporates assemblies having many optical fibers that must all be positioned to within a few microns, or inserted into fiber receptacles, or ferrules, this challenge often represents a significant manufacturing problem. The positioning of optical fibers is even more difficult when attempting to position the fibers in blind holes, or when attempting to automate the manufacturing process. 
     SUMMARY OF THE PRESENT INVENTION 
     The use of a vacuum to facilitate the insertion of optical fibers greatly simplifies the automated assembly process. In fact, the mechanical alignment tolerances typically experienced in fiber optic manufacturing may be reduced to hundreds of microns, so insertion of fibers into blind holes, typically a most challenging assembly using current approaches, may be easily automated. If conventional ferrules are used, a nozzle end or indent is typically used to guide the fiber. This invention eliminates the need for these nozzles or indented portions, and is even applicable to flat entrance holes. 
     In a typical application, an optical fiber is positioned for insertion into a hole within about 0.2 mm to 0.3 mm, and held about 50 mm from the end of the fiber. As the fiber is advanced toward the hole, the airstream converging into the hole acts to pull the fiber into alignment with the hole. Consequently, the fiber can be brought near the hole very rapidly, and because the fiber is flexible, the fiber will always go directly into the hole. Experiments have been conducted under microscope observation, and the principle has been repeatedly tested and the sequence observed in each assembly process. 
     In an application where a partial vacuum may be applied to an alignment plate having a number of alignment holes, a fiber clamp having multiple optical fibers may be positioned such that all of the optical fibers in the clamp may be inserted into the alignment plate simultaneously. As a result, large scale assembly of such delicate and flexible optical fibers, while maintaining a very high level of precision, may be achieved and represents a significant advantage over the current state of the art. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The novel features of this invention, as well as the invention itself, both as to its structure, its operation, and its method of use, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which like reference characters refer to similar parts, and in which: 
     FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention showing the vacuum region at the exit end of a plate formed with a number of fiber alignment holes; 
     FIG. 2 is a cross-sectional view of an alternate embodiment of the present invention showing the optical fiber as the vacuum draws the fiber into alignment for insertion into a strain relief plate having blind holes; and 
     FIG. 3 is a flow chart for the method of operation for the System For The Vacuum Assisted Insertion of Optical Fibers of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring initially to FIG. 1, a cross-sectional view of the preferred embodiment of the System for the Vacuum Assisted Insertion Of Optical Fibers of the present invention is shown and generally designated  100 . System  100  includes a plate  102  formed with a number of alignment holes  104  each having a diameter  106  for receiving an optical fiber  108  having a diameter  110 . 
     Each fiber  108  may be manufactured with a protective buffer sleeve  112  and extends from a fiber clamp  114 . The fiber  108  and buffer sleeve  112  extend from fiber clamp  114  a distance  116 , with a length  118  of buffer sleeve  112  being stripped so a portion of fiber  108  is exposed for insertion into the plate  102 . Fiber clamp  114  provides for the secure attachment of the fiber  108  into position and minimizes the movement of the fiber  108  during the assembly process and may be left in place to secure the fiber  108  within a final fiber optic product. Alternatively, fiber clamp  114  may be removed after assembly or once fiber  108  is secured in place with epoxy or RTV. 
     The diameter  106  of alignment hole  104  is typically 127 microns (127 μm) and just slightly larger than the diameter  110  of an optical fiber  108  as the diameter  110  of a typical optical fiber is approximately 125 microns (125 μm). As a result of this very small diameter  110 , and the need to precisely place the flexible fiber  108  within the alignment hole  104  of similar diameter  106 , insertion without using the present invention is particularly challenging, and often results in damage to the fiber  108 . 
     The length  118  of optical fiber  108  which extends from buffer sleeve  112  is typically 50 mm. Due to the flexible nature of optical fiber  108 , this 50 mm length of fiber is sufficient to allow insertion of the fiber  108  into alignment hole  104  in accordance with the present invention. This embodiment, however, is not intended as a limitation to the invention, rather, the present invention may be practiced in applications where no buffer sleeve  112  is used, as well as in systems where distance  118  approaches or equals zero. 
     As shown in FIG. 1, a vacuum system  120  is applied to exit surface  122  of plate  102  such that an airstream  124  (shown in dashed lines) is drawn into alignment hole  104  on face, or insertion side,  126  of the plate  102 . Vacuum system  120  includes a vacuum chamber  128  that is in fluid communication with a vacuum hose  130  which draws the airstream  124  in direction  132  into vacuum source  134 . It is to be appreciated that vacuum system  120  is merely exemplary to the present embodiment, and no limitation whatsoever is intended by the structure of the particular embodiment. Rather, the present invention includes all equivalents to system  120  which are capable of applying a partial vacuum to one or more alignment holes  104 . 
     Application of the present invention is shown in FIG. 1 as fiber clamp  114  is advanced in direction  136  such that fiber  108  moves toward face  126  of plate  104 . As fiber  108  approaches plate  104 , the end  138  of fiber  108  becomes exposed to airstream  124  as it rushes into alignment hole  104 . Due to the flexible nature of the fiber  108 , as the fiber further approaches plate  102 , the centering force resulting from airstream  124  brings the end  138  of fiber  108  into precise alignment with alignment hole  104 . As the fiber  108  is further advanced toward plate  102 , the end  138  of fiber  108  enters alignment hole  104  and is drawn towards exit surface  122  of plate  102 . 
     The flexible nature of the fiber  108 , in combination with the centering forces caused by the airstream  124  entering the alignment hole  104 , allows for the rapid insertion of fiber  108  into alignment hole  104 . The closer end  138  of fiber  108  comes to hole  104 , the larger the centering forces resulting from airstream  124  as it rushes into the hole  104 . Consequently, the insertion of fiber  108  into the alignment hole  104  in plate  102  may be done very quickly, and with very little attention to precision. 
     The present invention allows for the simultaneous insertion of multiple optical fibers  108  into plate  102 . As a result, the ordinarily time-consuming installation of optical fibers  108  into a plate  102  is reduced to one quick and problem free action of advancing the fiber  108  toward the alignment hole  104 . In fact, the high degree of precision ordinarily required in large scale manufacturing is virtually eliminated, allowing for a number of fibers  108  to be properly inserted into alignment holes  104  merely by positioning the fibers  108  adjacent the hole  104 , and allowing the centering forces caused by the airstream  124  to draw the fiber  108  into proper alignment with and into alignment hole  104 . 
     Only one alignment hole  104  has been shown with an airstream  124 . However, it is to be appreciated that such an airstream  124  exists for each alignment hole  104  exposed to vacuum system  120 , but these additional airstreams  124  have been omitted from FIG. 1 for clarity. 
     FIG. 1 also shows the position of a fiber  140  with buffer sleeve  142  once it has been drawn into alignment hole  144 . In this instance, fiber  140  extends past plate  102  a distance  146 . It is to be appreciated that the present invention provides for the insertion of fiber  140  into alignment hole  144  to any distance  146 , with the end  148  extending past exit surface  122 , positioned flush with exit surface  122 , or recessed within alignment hole  144 . 
     While the description of the present invention has included a plate  102  formed with alignment holes  104 , it is to be appreciated that the present invention is useful for the insertion of an optical fiber  108  into any closely-sized receptacle. For example, the present invention may be used to insert optical fibers into a ferrule (not shown). 
     Referring now to FIG. 2, a cross-sectional view of an alternate embodiment of the System for the Vacuum Assisted Insertion Of Optical Fibers of the present invention is shown and generally designated  200 . Plate  202  is formed with a number of alignment holes  204 ,  206 ,  208  which extend from the face  210  of plate  202  to an exit surface  212 . A vacuum chamber  214  provides a partial vacuum through tubing  216  as air is drawn in direction  218 . As discussed above in conjunction with FIG. 1, the partial vacuum caused in chamber  214  creates an airstream (not shown this Figure) at the face  210  of alignment hole  204 . 
     In the present embodiment, a strain relief plate  220  is provided which is formed with a number of bores  222  sized to receive a fiber  224  and buffer sleeve  226 . It is to be appreciated that a buffer sleeve  226  is not required, however, and the present invention may be practiced with fibers  108  and  224  having no buffer sleeves  112  and  226 . Each bore  222  in strain relief plate  220  extends from the entrance surface  225  to exit surface  227 , and has a diameter  228  to receive buffer sleeve  226  having a diameter  230 . The diameter  230  of a typical buffer sleeve  226  is 245 microns (245 μm) and the diameter  228  of a typical bore  222  is 0.635 millimeters. As a result, there is a sufficient opening  232  to allow sufficient air around buffer sleeve  226  and into bore  222  to create the airstream (not shown this Figure) for drawing fiber  224  into alignment hole  204 . As fiber  224  is advanced in direction  234 , the airstream (not shown this Figure) draws fiber  224  into alignment hole  204  as discussed above. 
     A strain relief plate  220  is particularly useful in circumstances where the movement of fiber  224  would corrupt the precise alignment of the fiber. Also, the larger strain relief plate  214  may be necessary because of the difficulty in drilling precise alignment holes  204  with very long aspect ratios. When a strain relief plate  220  is used in conjunction with plate  204 , it is particularly difficult to insert fibers  224  into alignment holes  204  as these holes are considered “blind” since they are not visible during the insertion process. 
     Fiber  236  is shown fully inserted into alignment hole  238  in plate  202  with buffer sleeve  240  extending into bore  222  in strain relief plate  220 . From this Figure it can be appreciated that a fiber  236  may be inserted into alignment hole  238  without the fiber  236  being equipped with a buffer sleeve  240 . Rather, the airstream will be sufficiently powerful to draw the flexible fiber  236  into alignment hole  238  for proper positioning near exit surface  212 . Once in position, the fiber  236  may be secured in place using a fiber clamp, such as clamp  114  shown in FIG. 1, or with an adhesive  242 , such as epoxy. 
     METHOD OF THE INVENTION 
     Referring now to FIG. 3, a flow chart of the Method For The Vacuum Assisted Insertion of Optical Fibers of present invention is shown and generally designated  300 . Method  300  begins with first step  302  which includes the positioning of an optical fiber adjacent the face, or insertion side, of a fiber alignment hole. Once the optical fiber is positioned adjacent the face of an alignment hole, next step  304  includes the application of a partial vacuum to the exit side of the alignment hole creating an airstream to pass from the face of the alignment hole, through the alignment hole, and exiting from the exit side of the alignment hole. 
     Once the partial vacuum is applied to the alignment hole, the optical fiber is advanced toward the alignment hole in step  306 . Because of the partial vacuum, the airstream provides a centering force to the fiber as it approaches the alignment hole, and this centering force draws the optical fiber into precise alignment with the alignment hole. 
     Once the fiber is aligned with the alignment hole in step  306 , the optical fiber is advanced further towards and into the alignment hole in step  308 . The optical fiber may be advanced through alignment hole to its desired position until the end of the fiber is flush with the exit side of the plate, extending through the plate a desired distance, or recessed within the plate. 
     Once the fiber is positioned as desired in the alignment hole in step  308 , the vacuum source may be removed from the exit side of the plate in step  310 , and the optical fiber is secured in place. The fiber may be secured in place using a clamp or an adhesive, as discussed more thoroughly above. Once positioned and secured, the optical Fiber can then be located with precision for further connection to an optical network. 
     The order of the steps discussed above and shown in FIG. 3 are merely exemplary of a preferred embodiment of the present invention. Thus, the particular order is not to be construed as a limitation on the scope of the invention, rather, the method steps may be performed in any order so long as the vacuum is applied to the exit side of the alignment hole and the fiber is drawn into the alignment hole. For example, the vacuum may be applied continuously during the insertion process, including before, during and after the insertion of the optical fiber into the fiber alignment hole. Also, the vacuum may be left in place against the exit side of the alignment hole while the fibers are secured in place, such as by clamping or by applying epoxy. 
     While the particular System and Method For The Vacuum Assisted Insertion of Optical Fibers as herein shown and disclosed in detail is fully capable of achieving the objects and providing the benefits herein before described, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design, or the order of method steps, herein shown other than as described in the appended claims.