Abstract:
A fiber optic connector includes a ferrule. The ferrule includes an inner piece including silica and an outer piece including ceramic. The outer piece surrounds the inner piece and the inner piece extends beyond an end of the outer piece by a distance of at least 10 micrometers.

Description:
RELATED CASES 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 61/752,697 filed on Jan. 15, 2013 the content of which is relied upon and incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    Aspects of the present disclosure relate generally to fiber optic connectors, ferrules that may be used with fiber optic connectors, and methods of manufacturing ferrules and connectors. 
         [0003]    Ferrules in use today are often made of zirconia because zirconia ferrules tend to be particularly durable and the manufacturers can produce zirconia ferrules with high-precision dimensional tolerances at very low cost. The color of zirconia ferrules is generally a distinct glossy white and their overall appearance is generally the same, regardless of the manufacturer. 
         [0004]    Mechanical polishing is typically used when manufacturing fiber optic connectors with ferrules and associated optical fibers because mechanical polishing is an industry-proven way to achieve a fiber and ferrule geometry that is compliant with current international standard specifications, such as having a fiber height of ±100 nm from the ferrule end face, depending on connector type and radius of curvature and apex offset. Mechanical polishing is also capable of removing excess epoxy on the end face. 
         [0005]    One problem with zirconia ferrules is that the zirconia may not survive direct contact with high quantities of laser power. Contact with the laser beam may cause micro-cracking of the zirconia. Therefore it is generally difficult to laser process a short glass fiber protruding from the zirconia ferrule. As such, conventional laser-cut fibers have a significant length of the fibers protruding from the end face of a zirconia ferrule to prevent damage to the zirconia. This length is typically greater than 50 μm and since the industry standard for fiber protrusion is +/−100 nm, additional processing is typically needed. 
         [0006]    A need exists for a ferrule system that facilitates laser processing of optical fibers at a close distance to the ferrule, such as a distance less than 50 μm from the end face of the ferrule. 
       SUMMARY 
       [0007]    Inventive and innovative technology disclosed herein includes a fiber optic connector having a ferrule configured to facilitate a manufacturing process to achieve industry-standard specifications for the geometry of the end face of the ferrule on a terminated optical cable assembly. The ferrule includes two or more pieces. 
         [0008]    In some embodiments, an outer piece of the ferrule includes zirconia to provide strength and durability for the ferrule, while maintaining the overall appearance of a conventional ferrule. An inner piece of the ferrule includes a material, such as fused silica, that melts and/or ablates in a manner similar to silica-based optical fibers. The ferrule facilitates laser-forming and processing of the optical fiber in one process step, and the inner piece may subsequently be inserted into and secured within the outer piece of the ferrule. 
         [0009]    One embodiment relates to a method of manufacturing a fiber optic connector. The method includes a step of stripping an optical fiber of one or more polymeric coatings to expose a glass cladding of the optical fiber. The method includes another step of inserting the optical fiber into an inner piece of a ferrule, where the inner piece includes silica. Further, the method includes steps of processing the optical fiber in the inner piece of the ferrule using a laser and, subsequent to the processing step, inserting the inner piece of the ferrule into an outer piece of the ferrule. The outer piece includes a ceramic material that is more durable than the inner piece. 
         [0010]    Another embodiment relates to a ferrule for a fiber optic connector, which includes an inner piece including a first material and an outer piece including a second material. The outer piece surrounds the inner piece, and the inner piece extends beyond an end of the outer piece. Yet another embodiments relates to a fiber optic connector including such a ferrule, where the inner piece extends beyond the end of the outer piece by a distance of at least 10 micrometers. 
         [0011]    Additional features and advantages are set forth in the Detailed Description that follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following Detailed Description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0012]    The accompanying Figures are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the Detailed Description serve to explain principles and operations of the various embodiments. As such, the disclosure will become more fully understood from the following Detailed Description, taken in conjunction with the accompanying Figures, in which: 
           [0013]      FIG. 1  is a side sectional view of an inner piece of a ferrule according to an exemplary embodiment. 
           [0014]      FIG. 2  is a side sectional view of an outer piece configured to support the inner piece of  FIG. 1  according to an exemplary embodiment. 
           [0015]      FIG. 3  is a side sectional view of fiber optic connector according to an exemplary embodiment. 
           [0016]      FIGS. 4-5  are side schematic views of the inner piece of  FIG. 1  with an optical fiber therein, depicting two different depth of focus and spot-size setups for laser processing the optical fiber according to an exemplary embodiment. 
           [0017]      FIG. 6  is a schematic diagram of a manufacturing assembly including a galvanometer to scan a focused laser beam for processing of the optical fiber according to an exemplary embodiment. 
           [0018]      FIG. 7  is a diagram of an energy distribution of a laser beam shown from a diffractive optical element. 
           [0019]      FIG. 8  is a side sectional view of a ferrule for a fiber optic connector according to another exemplary embodiment. 
           [0020]      FIG. 9  is a side sectional view of the ferrule of  FIG. 8  after the ferrule has been further processed according to an exemplary embodiment. 
           [0021]      FIG. 10  is a side sectional view of a ferrule for a fiber optic connector according to yet another exemplary embodiment. 
           [0022]      FIG. 11  is a side sectional view of a ferrule for a fiber optic connector according to another exemplary embodiment. 
           [0023]      FIG. 12  is a side sectional view of the ferrule of  FIG. 9  with a stub of an optical fiber extending therefrom according to another exemplary embodiment. 
           [0024]      FIG. 13  is a side sectional view of a multi-fiber ferrule according to an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Before turning to the Figures, which illustrate exemplary embodiments now described in detail, it should be understood that the present inventive and innovative technology is not limited to the details or methodology set forth in the Detailed Description or illustrated in the Figures. For example, as will be understood by those of ordinary skill in the art, features and attributes associated with embodiments shown in one of the Figures may be applied to embodiments shown in others of the Figures. 
         [0026]    Referring to  FIGS. 1-2 , a ferrule  110  (e.g., composite ferrule, two-piece ferrule) includes an inner piece  112  (e.g., inner ferrule, insert, first structure; see  FIG. 1 ) and an outer piece  114  (e.g., exterior ferrule, shell, second structure; see  FIG. 2 ). The inner piece  112  includes a bore  118  for an optical fiber  116  ( FIG. 3 ) and the inner piece  112  is sized and configured to fit into an interior passage  120  (e.g., bore) defined by the outer piece  114 . In some embodiments, the outer piece  114  includes a durable ceramic (e.g., zirconia) or other material (e.g., polymer), and the inner piece  112  includes a silica-based material and/or glass. The inner piece  112  may have ablation and melt characteristics in common with cladding of the optical fiber  116 , where the optical fiber  116  has a glass transmission core surrounded by the cladding. 
         [0027]    According to an exemplary embodiment, the optical fiber  116  may be installed in the inner piece  112 , laser processed, and then (i.e., subsequently thereto) inserted into the outer piece  114 . According to an exemplary embodiment, the radius of curvature and apex offset of the optical fiber  116  (on the end thereof) may be controlled by the laser process and the height of the optical fiber  116  relative to the adjoining end face  140  ( FIG. 4 ) of the ferrule  110  is within ±100 nanometers (nm). 
         [0028]    The relative height H of the inner piece  112  to the outer piece  114  (see  FIG. 9 ) may not be particularly significant, in some such embodiments, because the optical fiber  116  is processed within the inner piece  112  and ready for use, prior to insertion of the inner piece  112  (and optical fiber  116 ) into the outer piece  114 . In other embodiments, sufficient relative height H of the inner piece  112  to the outer piece  114  may facilitate laser processing without damaging the outer piece  114 , such as with embodiments in which the optical fiber  116  is at least partially laser processed (e.g., laser polished) while the inner piece  112  is positioned in the outer piece  114 . 
         [0029]    According to an exemplary embodiment, the material of the inner piece  112  is primarily (e.g., at least 50% by volume, at least 70% by volume, consists essentially of, consists entirely of) fused silica or another material that will process in a manner similar to the optical fiber  116 . For example, if the optical fiber  116  is made from a material other than glass, the inner ferrule material  112  could be selected to match the material of the optical fiber  116 . Accordingly, the material of the inner piece  112  of the ferrule  110  is selected and configured to melt and/or ablate using a laser of a particular wavelength and power that may also cut (i.e. cleave), shape (i.e. machine), bond (i.e. partially melt), and/or polish the optical fiber  116 . 
         [0030]    Referring to  FIG. 3 , once the optical fiber  116  and ferrule  110  are fully assembled and processed, the ferrule  110  may be used in a fiber optic connector  122 . The connector  122  may include a housing  124 , a seat or holder  128  for the ferrule  110 , a lead-in tube  126 , a boot  132 , and/or a spring  130  between the ferrule holder  128  and the housing  124 . The connector  122  may be attached to an end of the optical fiber  116 , which may be carried within the jacket  136  of a fiber optic cable  134 . The optical fiber  116  may be a single mode optical fiber, a multi-mode optical fiber, a multi-core optical fiber, one of multiple optical fibers, one of multiple optical fibers forming a ribbon of optical fibers, or another type or configuration of optical fiber. As shown in  FIG. 13 , concepts and features disclosed herein may be used with a multi-fiber ferrule  510 , where the insert(s) (or inner piece  512 ) includes bores for multiple optical fibers  516 . 
         [0031]    Referring now to  FIGS. 4-5 , once an appropriate material for the inner piece  112  of the ferrule  110  has been selected, a laser beam  138  may be shaped and focused at an appropriate angle and position relative to the fiber/ferrule end face  140  intersection. The laser beam  138  may be shaped using custom optical systems or diffractive optical elements (e.g., lens  142 ). Using a pulsed- or continuous-wave beam  138 , energy is delivered to the optical fiber  116  and inner piece  112  of the ferrule  110 . The energy may melt and/or ablate materials of the optical fiber  116  and inner piece  112 , simultaneously, for cutting, for bonding, for polishing, to achieve a desired shape, or for other reasons. 
         [0032]    Silica may be used as a material of the inner ferrule  112  because silica may share common material properties with silica optical fibers having germania-doped cores. The optical fiber  116  may be bonded to the ferrule  110  using any method that yields acceptable results. In some embodiments, the fiber  116  is bonded to the ferrule  110  using a CO 2  laser, such as by laser welding; and both forming and bonding the fiber  116  may be accomplished with a common laser (e.g., beam of same wavelength), such as during the same manufacturing step. The resulting assembly of the ferrule  110  and the optical fiber  116  may then be placed into a port or fixture that registers the position of the ferrule  110 . With understanding of the position of the ferrule  110  (and components thereof) a CO 2  laser beam may be shaped, focused, and aligned relative to the ferrule  110  for further processing. 
         [0033]    Referring now to  FIGS. 6-7 , for some laser/fiber-ferrule combinations it may be preferable to have relative motion between the laser beam  138  and fiber-ferrule assembly  112 / 116 . An example would be to focus the laser beam  138  to a point and then sweep the laser beam  138  back and forth across the fiber-ferrule assembly  112 / 116 , cutting and polishing the ferrule  112  and optical fiber  116 . A 1-D galvanometer  144  scanning system or a laser-scanning head may be used to achieve this relative motion (see  FIG. 6 ). In other embodiments, a mirror may be attached to a linear stage, instead of a rotating galvanometer  144 . The focal length of the focusing lenses  142  would be long enough to produce a depth of focus, to thereby produce a substantially flat ferrule/fiber end face  140 , although the ferrule end face  140  and fiber  116  may not be perfectly flat. For example, the substantially flat ferrule/fiber end face  140  may have a radius of curvature of about 1 to 30 mm, or more preferably about 5 to 25 mm depending on the connector type. 
         [0034]    The laser is selected to produce enough energy to maintain an acceptable energy density. For example, in some embodiments the energy distribution of the laser beam  138  is at least about 10,000 W/mm 2 . A diffractive optic that can shape the energy distribution is another viable alternative to sweeping the beam  138 . Companies such as Holo-Cor (a division of Laser Components) may provide the ability to produce a uniform energy distribution and shape (see, e.g., beam spot of  FIG. 7 ) the beam  138  into a block that is wider than the ferrule  110 . A diffractive optic made out of ZnSe may be made to produce this energy distribution at focus, given a standard laser beam input (other diffractive optic materials and geometries are contemplated). The distribution can then be pulsed to cut and polish the fiber-ferrule assembly  112 / 116  without the need to translate the beam  138  or the fiber-ferrule assembly  112 / 116 . The laser and optics may be sized to match the necessary energy distribution to properly cut and polish the ferrule  110 . A 150 μm by 300 μm energy distribution is shown in  FIG. 7  as an example of such an energy distribution. 
         [0035]    An exemplary product and process may include stripping a 250 μm acrylate coating off of the optical fiber  116  using a 9.3- or 10.6-μm CO 2  laser (e.g., the laser having at least 400 W capacity), then inserting the prepared fiber  116  into the inner piece  112  of the ferrule  110  to a predetermined position. The end face  1140  of the ferrule  110  may already be positioned appropriately relative to the laser. The laser beam  138  would then thermally form the end face  140  of both the optical fiber  116  and the ferrule  110  simultaneously, and bond them together in the radial and/or longitudinal axis of the optical fiber  116 . In some embodiments, the resulting geometry of the end face  140  and the visual quality is compliant with industry standards. 
         [0036]    In other contemplated embodiments, the ferrule  110  may be rotated during laser processing to achieve a uniform shape of the end face  140 . Such rotation may be a partial rotation, a rocking motion, a full 360-degree turn, and/or a continuous spinning rotation. 
         [0037]    Once the inner piece  112  of the ferrule  110  and the optical fiber  116  have been processed, the assembly  112 / 116  may be inserted into the outer piece  114  of the ferrule  110 , positioned and aligned, and locked into place with any acceptable means. Some such means include chemical adhesives (e.g., thermoplastic, thermoset) and/or mechanical interlocks (e.g., friction fit, flange or latch). The optical fiber  116  position relative to the outer diameter of the outer piece  114  of the ferrule  110  may be adjusted before locking the inner piece  112  of the ferrule  110  in place, to provide concentricity of the optical fiber  116  within the ferrule  110 . 
         [0038]    Referring now to  FIGS. 8-9 , a fiber and glass insert  212  may be preassembled into a zirconia outer ferrule  214  of a ferrule  210 , such as with some length H of the insert  212  protruding from the end face of the zirconia ferrule  214 . In such embodiments, an optical fiber  216  may be partially processed, such as bonded to the glass insert  212 , but not fully processed, such as being polished and ready for use. The laser cut/polish process may then cut the glass insert  212  and optical fiber  216  simultaneously, as close to the zirconia outer ferrule  214  as possible without damaging the zirconia outer ferrule  214 , such as a distance of less than 5 mm but greater than about 10 μm. Once further laser processed, as shown in  FIG. 9 , the protruding portion of the glass insert  212  and optical fiber  216  may meet precision industry standard specifications such as being within ±100 nm of the end face of the ferrule  210 . 
         [0039]    Referring to  FIG. 10 , a short glass inner ferrule  312  may be a counter-bored into a zirconia outer ferrule  314  of a composite ferrule  310 . The counter-bore may limit movement of the inner ferrule  312  during mating loads. Referring now to  FIG. 11 , a chamfered zirconia outer ferrule  414  with bevel  420  may allow a laser to get closer to a zirconia face thereof without damaging a face  418  thereof, resulting in a shorter protrusion length of an inner ferrule  412  of such a ferrule  410 . Both the ferrules  310 ,  410  may be processed preassembled, as in  FIG. 8 , or as previously discussed, may be processed unassembled, cut, and then subsequently bonded. Further, the bevel  420  of  FIG. 11  and/or shorter inner ferrule  312  and counter-bore of  FIG. 10  may be incorporated in alternative embodiments of the other ferrules  110 ,  210 ,  510  disclosed herein. 
         [0040]    Referring to  FIG. 12 , the two-piece ferrule  210  is processed with a short fiber stub  218  protruding from the back of the ferrule  210 . The processed stub  218  is splice-ready and may be fusion spliced and/or used in a mechanical splice package, such as UNICAM® manufactured by Corning Cable Systems (a subsidiary of Corning Incorporated) of Hickory, N.C. As discussed above, embodiments disclosed herein may be used with single-fiber connectors, as shown in  FIG. 3 ; or as shown in  FIG. 13 , with ferrules  510  of multi-fiber connectors. 
         [0041]    Advantages of technology disclosed herein, in some embodiments, include reduction and/or elimination of mechanical polishing of the optical fiber  116  and ferrule end face  140 ; reduction and/or elimination of consumables for mechanical polishing; reduction of overhead costs to manage polishing equipment and consumables; reduction of process variation, defects, and scrap; reduction in manufacturing cycle time; the ability to implement a single connector manufacturing process using automated lasers, reduction in process steps for connector termination, reduction in labor content per connector termination, reduction in operator influence on process outcome, improved end face  140  visual quality and geometry, process flexibility, maintaining of overall appearance of current ferrules/connectors. 
         [0042]    The construction and arrangements of the ferrules and fiber optic connectors, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various members, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present inventive and innovative technology.