Abstract:
A fiber optic connector including a ferrule surrounding an optical fiber and a hub engaging the ferrule. The hub includes a front portion having first and second surfaces and first and second tapered contact regions extending from the first and second surfaces to a front face. A housing includes an anti-rotation seat configured to engage the first and second surfaces, the anti-rotation seat including first and second angled contact surfaces positioned at a front of the anti-rotation seat. A spring within a chamber of the housing biases the ferrule through a bore in the front of the housing. The first tapered contact region of the hub engages the first contact surface, and the second tapered contact region engages the second contact surface when the hub and ferrule are in a first rotational position so that the optical fiber is maintained at a known orientation with respect to the connector. The tapered contact regions are planar surfaces sized smaller than the angled contact surfaces.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation of non-provisional patent application Ser. No. 10/942,545, filed on Sep. 16, 2004, which claims priority to provisional patent application Ser. No. 60/562,696, filed on Apr. 14, 2004, the disclosures of which are incorporated by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to fiber optic connectors for use in an optical fiber signal transmission system, and to methods for assembling such fiber optic connectors.  
       BACKGROUND  
       [0003]     Fiber optic cables are used in the telecommunication industry to transmit light signals in high-speed data and communication systems. A standard fiber optic cable includes a fiber with an inner light transmitting optical core. Surrounding the fiber is an outer protective casing.  
         [0004]     A fiber terminates at a fiber optic connector. Connectors are frequently used to non-permanently connect and disconnect optical elements in a fiber optic transmission system. There are many different fiber optic connector types. Some of the more common connectors are FC and SC connectors. Other types of connectors include ST and D4-type connectors.  
         [0005]     A typical SC fiber optic connector includes a housing having a front end positioned opposite from a rear end. The front end of the SC connector housing is commonly configured to be inserted within an adapter. An example adapter is shown in U.S. Pat. No. 5,317,663, assigned to ADC Telecommunications, Inc. The SC connector typically further includes a ferrule that is positioned within the front and rear ends of the housing, and adjacent the front end. The ferrule is axially moveable relative to the housing, and is spring biased toward the front of the connector. The fiber optic cable has an end that is stripped. The stripped end includes a bare fiber that extends into the connector and through the ferrule.  
         [0006]     A connector, such as the connector described above, is mated to another connector within an adapter like the adapter of U.S. Pat. No. 5,317,663. A first connector is received within the front portion of the adapter, and a second fiber is received within the rear portion of the adapter. When two connectors are fully received within an adapter, the ferrules (and hence the fibers internal to the ferrule) contact or are in close proximity to each other to provide for signal transmission between the fibers. A further SC connector is shown in U.S. Pat. No. 6,428,215, assigned to ADC Telecommunications, Inc. Another connector and mating adapter is shown in U.S. Pat. No. 6,142,676, also assigned to ADC Telecommunications, Inc.  
         [0007]     Rotational misalignment of a ferrule with respect to a connector axis can cause mis-engagement between the ferrule and a ferrule of another connector, thereby contributing to signal loss. This problem is especially acute for angled physical contact connectors. An angled physical contact (APC) connector includes a ferrule and fiber with end faces that are polished to a non-perpendicular angle (for example, 8 degrees to a perpendicular plane) with respect to the longitudinal axis of the connector. APC connectors are discussed in U.S. Pat. No. 5,734,769, assigned to ADC Telecommunications, Inc. The orientation of the end face must be maintained with a high degree of precision so that the angled end face of the optic fiber and associated ferrule correctly engage an end face of an optic fiber and associated ferrule of another angled physical contact connector. Even a few degrees of misalignment can cause significant signal loss.  
       SUMMARY  
       [0008]     The present invention concerns fiber optic connectors having a spring biased ferrule and hub assembly held within the connector. The hub includes an anti-rotation portion which engages a complementary-shaped anti-rotation seat of the connector. The anti-rotation seat further includes at least first and second contact surfaces, and the anti-rotation portion of the hub includes first and second mating contact surfaces which maintain the end face of the optic fiber and associated ferrule at a specific rotational angle with respect to the longitudinal axis of the connector when the ferrule is in its resting position. Further, when the ferrule is pushed back into the connector and then allowed to return to its resting position, the contact surfaces re-engage to return the end face of the optic fiber and associated ferrule to the desired orientation. The contact surfaces are sized and shaped to allow the ferrule to return to its resting position without damaging the connector parts, such as due to sharp edges. Also, the contact surfaces are sized and shaped to only allow the ferrule to extend from the connector within a range that allows connection to other connectors, so that the ferrule is not extended too far or too little when mated to another connector.  
         [0009]     One aspect of the invention relates to a fiber optic connector including an optical fiber, a ferrule surrounding the optical fiber, a hub retainably engaging the ferrule, wherein the hub includes a front portion having first and second surfaces, and first and second tapered contact regions at an angle with respect to a longitudinal axis of the connector, a housing defining an anti-rotation seat configured to engage the first and second surfaces of the front portion of the hub, the anti-rotation seat including first and second contact surfaces positioned at a front of the anti-rotation seat adjacent a bore defined by the housing through which the ferrule extends, and a spring disposed within a chamber defined by the housing and coupled to the anti-rotation seat, the spring biasing the ferrule through the bore of the housing, wherein the first tapered contact region of the hub engages the first contact surface and the second tapered contact region engages the second contact surface when the hub and ferrule are in a first rotational position relative to the housing so that an end of the optical fiber is maintained at a known orientation with respect to the longitudinal axis of the connector. The tapered contact regions on the hub are preferably planar surfaces, preferably smaller than the contact surfaces of the housing. In one preferred embodiment, three tapered contact regions and three contact surfaces are provided.  
         [0010]     Another aspect of the invention relates to a hub and ferrule assembly for a fiber optic connector including a ferrule configured to surround an optical fiber, and a hub retainably engaging the ferrule, wherein the hub includes a front portion having first and second surfaces and first and second tapered contact regions at an angle with respect to a longitudinal axis extending through a center of the hub and ferrule assembly, wherein the first tapered contact region is positioned to engage a first contact surface on the fiber optic connector and the second tapered contact region is positioned to engage a second contact surface on the fiber optic connector. The tapered contact regions on the hub are preferably planar surfaces, preferably smaller than the mating contact surfaces in the connector. In one preferred embodiment, three tapered contact regions are provided.  
         [0011]     Yet another aspect of the invention relates to a fiber optic connector housing including an exterior body configured to be received in a fiber optic adapter, a cavity defined by a rear portion of the connector housing, an anti-rotation seat coupled to the cavity, the anti-rotation seat including a plurality of longitudinally extending surfaces, and first and second angled contact surfaces positioned at a front of the anti-rotation seat adjacent a bore; the first and second angled contact surfaces being spaced apart around a longitudinal axis of the connector housing. In one preferred embodiment, three contact surfaces are provided.  
         [0012]     Another aspect of the invention relates to a fiber optic connector including an optical fiber, a ferrule surrounding the optical fiber, a hub retainably engaging the ferrule, the hub including an anti-rotation portion, a housing defining an anti-rotation seat configured to engage the anti-rotation portion of the hub, a spring disposed within a chamber defined by the housing and coupled to the anti-rotation seat, the spring biasing the ferrule through the bore of the housing, and an alignment arrangement formed by the connector, the alignment arrangement including first and second tapered contact regions formed on one of the hub and the housing, and also including first and second contact surfaces formed on the other of the hub and the housing, wherein the first tapered contact region engages the first contact surface and the second tapered contact region engages the second contact surface when the hub and ferrule are in a first rotational position relative to the housing so that an end of the optical fiber is maintained at a known orientation with respect to the longitudinal axis of the connector. The tapered contact regions are preferably planar surfaces, and preferably smaller than the contact surfaces. In one preferred embodiment, three tapered contact regions and three contact surfaces are provided.  
         [0013]     Yet a further aspect of the invention relates to a method for using a fiber optic connector comprising steps of: providing a ferrule surrounding an optical fiber with a hub retainably engaging the ferrule, the hub including opposing first and second tapered contact portions; providing a housing including a first contact surface positioned to engage the first tapered contact portion and a second contact surface positioned to engage the second tapered contact portion; pushing the ferrule back to disengage the first and second tapered portions of the hub from the first and second contact surfaces of the housing; and releasing the ferrule so that the first tapered contact portion engages the first contact surface and the second tapered contact portion engages the second contact surface, thereby retaining the optical fiber at a known orientation with respect to the longitudinal axis of the connector. The tapered contact regions are preferably planar surfaces, and preferably smaller than the contact surfaces. Preferably, three tapered contact portions and three contact surfaces retain the optical fiber at the known orientation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective few of an embodiment of a fiber optic connector in accordance with the present invention.  
         [0015]      FIG. 2  is an exploded view in perspective of the connector shown in  FIG. 1 .  
         [0016]      FIG. 3  is a cross-sectional side view of the connector of  FIG. 1 .  
         [0017]      FIG. 4  is an enlarged cross-sectional side view of the front end of the connector of  FIG. 3 .  
         [0018]      FIG. 5  is a rear end view of the front housing of the connector.  
         [0019]      FIG. 6  is a front end view of the front housing of the connector.  
         [0020]      FIG. 7  is a front end view of the hub of the connector.  
         [0021]      FIG. 8  shows in exploded view one pair of the mating contact surfaces in greater detail. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]     Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0023]      FIGS. 1-8  illustrate an example embodiment of a connector  100  made in accordance with the present invention. The connector  100  is of the SC type. The connector  100  includes a front housing  110 , a rear housing  140 , and a boot  150  with a bore  152 . A grip  156  fits over the front housing  110 , and the rear housing  140 . The boot  150  fits into a rear end  158  of the grip  156 . Also included in the connector  100  is a hub/ferrule assembly  120  with a hub  122  and a ferrule  124 . The hub  122  includes an anti-rotation portion  128  and an elongated cylindrical rear portion  123 . The hub  122  is connected to the ferrule  124 , such as with adhesive or an interference fit. A spring  130  is also provided. A fiber optic cable  101  is shown including a fiber  102  and a jacket  103 .  
         [0024]     The connector  100  is tunable by rotating the front housing  110  relative to the rear housing  140 . Once the grip  156  is positioned over the front and rear housing  110 ,  140 , the front housing  110  can no longer be rotated relative to the rear housing  140 . In order to rotate the front housing  110  relative to the rear housing  140 , the hub  122  must be pushed back out of engagement with the front housing  110 .  
         [0025]     Disposed within the rear housing  140  is an anti-rotation seat  112  and a cavity  114 . The anti-rotation portion  128  of the hub  122  is slidingly engaged along the longitudinal axis  200  in the anti-rotation seat  112 . The anti-rotation portion  128  of the hub  122  includes an exterior surface of hub  122  extending parallel to the axis  200  having a configuration which does not allow rotation when the anti-rotation portion  128  of the hub  122  is mated with the anti-rotation seat  112 . In the illustrated embodiment, the anti-rotation portion  128  of the hub  122  includes a plurality of surfaces defining a bread loaf shape. In particular, three planar and perpendicularly arranged surfaces  129  are provided defining generally three sides of the hub  122 . A fourth surface  131  is generally rounded (see  FIG. 7 ), thereby defining the bread loaf shape. The anti-rotation seat  112  is provided with a similar profile for mating with the anti-rotation portion  128 . Further details regarding the tunability feature and the anti-rotation feature of the connector  100  are described and shown in U.S. Pat. No. 6,428,215, the disclosure of which is hereby incorporated by reference.  
         [0026]     The spring  130  surrounds the elongated cylindrical rear portion  123  of the hub  122 . The spring is captured between the anti-rotation portion  128  and a surface  146  of the rear housing  140 . The spring  130  functions to bias the ferrule  124  in a forward direction through a front bore  116  of the front housing  110 . The elongated cylindrical rear portion  123  of the hub  122  extends into the cavity  114  of the front housing  110 .  
         [0027]     The complementary fit between the anti-rotation seat  112  and the anti-rotation portion  128  is designed to maintain the ferrule  124  in a specified orientation with respect to the longitudinal axis  200  of the connector  100 . However, small variations in tolerances between the anti-rotation seat  112  and the anti-rotation portion  128  may cause the ferrule  124  to become misaligned a few degrees with respect to the longitudinal axis  200 , thereby causing the face  125  of the ferrule  124  to be slightly misaligned, increasing the insertion loss when the connector  100  is mated to another connector through an adapter. Such misalignment can occur during initial assembly. Such misalignment can also occur when an end face of an APC connector is mated with an end face of another APC connector, and then one connector is removed. The spring bias returns the ferrule  124  of the hub  122  to the front position. The longitudinally extending surfaces of the anti-rotation portion  128  and the anti-rotation seat  112  maintain the general rotational positions of the hub  122  and the front housing  110 , but small variations may be introduced. If not corrected, the next connection of the connector may result in rotationally misaligned end faces. The angled end face  125  is shown in  FIGS. 3 and 4 .  
         [0028]     Referring now to  FIGS. 3-8 , the alignment features of connector  100  are shown. The front housing  110  includes a plurality of contact surfaces  220 ,  221 ,  222 . The contact surfaces  220 ,  221 ,  222  on the housing  110  engage mating contact regions  214 ,  215 ,  216  on the hub  122 . Preferably the contact surfaces  220 ,  221 ,  222  are angled at a 45-degree angle relative to the longitudinal axis  200 . The contact regions  214 ,  215 ,  216  on the hub  122  are smaller planar surfaces also angled at a 45-degree angle relative to the longitudinal axis  200 .  
         [0029]     In the preferred embodiment, three mating contact surfaces  220 ,  221 ,  222  and contact regions  214 ,  215 ,  216 , are provided on the connector  100 . Two mating surfaces can also be utilized, if desired. Alternatively, more than three mating surfaces can be provided. Unused mating surfaces can be provided if greater numbers of surfaces on one of the hub  122  or the front housing  110  are provided. Depending on the relative positions on the hub  122  and the front housing  110 , only three of the contact regions  214 ,  215 ,  216  are used. The other contact regions  214   a ,  215   a ,  216   a  are not used unless the connector is tuned.  
         [0030]     As shown, the contact surfaces  220 ,  221 ,  222  are equally spaced about the longitudinal axis  200 . Similarly, the contact regions  214 ,  215 ,  216  have center portions that are also equally spaced about the longitudinal axis  200 .  
         [0031]     By engagement of the respective pairs of angled contact surfaces and contact regions, alignment of the ferrule  124  relative to the housing  110  is provided. This alignment is greater than can be provided by the longitudinally extending sliding surfaces of the anti-rotation portion  128  and the anti-rotation seat  112 .  
         [0032]     As shown, the contact regions  214 ,  215 ,  216  are smaller than the contact surfaces  220 ,  221 ,  222 . If the contact regions  214 ,  215 ,  216  were too large, such as if they are similarly sized relative to the contact surfaces  220 ,  221 ,  222 , small angle variations during manufacture could cause drastic variations in the amount of extension of ferrule  124 . If the ferrule  124  extended too far when mated to another connector, damage to the ferrules or connectors could occur. If the ferrule did not extend enough, poor signal transmission from connector to connector would result. Alternatively, if the contact regions  214 ,  215 ,  216  are quite small, such that a fairly sharp edge is defined, damage to the front housing  110  can occur, such as when relatively larger springs  130  are used. The connector could become damaged if the hub or housing is engaged with too much force by a sharp edge, such as in the case when plastic parts are used.  
         [0033]     As one example, the hub  122  is made from metal, such as F/N 001 nickel silver CDA 792, and the front housing  110  is made from plastic, such as F/N 001 Ul tem. Contact surfaces  220 ,  221 ,  222  are about 0.036 inches long at the midpoint (dimension A in  FIG. 5 ) and are angled 45 degrees +/−1 degree to the longitudinal axis  200 . Contact surfaces  220 ,  221 ,  222  are smaller at the ends, at about 0.014 inches (dimension B). The view of  FIG. 5  shows surfaces  220 ,  221 ,  222  at an angle. (Compare also to the cross-section of  FIG. 4 ). Dimensions A and B noted above are taken parallel to the direction of extension of each surface. See also  FIG. 8 .  
         [0034]     For an SC type connector in this example, it has been found that contact regions  214 ,  215 ,  216  of a length of about 0.0085 inches to 0.0100 inches (dimension C in  FIG. 7 ) at 45 degrees +/−1 degree to the axis  200  result in appropriate mating with the front housing  110 , without causing deformation of the front housing  110  or too much variation in the extension of the ferrule  124  as the angles on contact surfaces  220 ,  221 ,  222  vary plus or minus 1 degree. In  FIG. 7 , contact regions  214 ,  215 ,  216  are at an angle. Dimension C is parallel to the direction of extension. See also  FIG. 8 . This results in a variation of extension of the ferrule of 0.00130 inches. With an SC connector designed as noted above, an overall ferrule variation of extension of 0.014 inches is achieved. The dimension of 0.014 inches is an industry accepted ferrule variation resulting in proper connections with mating connectors.  
         [0035]     In the preferred embodiment, contact regions  214 ,  215 ,  216  are planar and smaller than contact surfaces  220 ,  221 ,  222 .  
         [0036]     Variations in the angle for the mating contact surfaces are possible. The illustrated example shows 45 degree angles from a plane transverse to the longitudinal axis. Other angles can be used such as 60 degrees. However, for the greater angles, greater variation in ferrule extension may be noticed as variations occur during manufacturing for the precise angles and locations of the mating contact surfaces.  
         [0037]     By utilizing three equally spaced contact surfaces  220 ,  221 ,  222 , mated with contact regions  214 ,  215 ,  216 , less tilting of the ferrule  124  relative to the longitudinal axis  200  occurs. The effect of three equally spaced mating surfaces is similar to a three-legged stool or a tripod. Three surfaces are advantageous over two, because they do not provide any centering effect in a direction parallel to the two surfaces. Increasing the number of mating surfaces can further reduce tilting effects if more than three surfaces are mated. It is to be appreciated that the angled surfaces on hub  122  are not all equally sized. However, the effect of having three of them ( 214 ,  215 ,  216  or  214   a ,  215   a ,  216   a ) mate with surfaces  220 ,  221 ,  222  is to create a tripod effect.  
         [0038]     Some fiber optic connectors are tunable by unseating the ferrule and associated hub from the anti-rotation seat. The ferrule and associated hub is pushed back from the resting position by pressing the ferrule back into the connector. The anti-rotation portion of the hub clears the complementary-shaped anti-rotation seat of the connector. In this position, the ferrule can be rotated about a connector axis to the desired rotational alignment that minimizes signal loss. The ferrule can then be released, allowing the anti-rotation portion of the hub to re-engage the anti-rotation seat, thereby preventing further rotation that may cause the connector to become un-tuned. In a connector of this style, the contact surfaces  220 ,  221 ,  222  would similarly engage the contact regions  214 ,  215 ,  216  to align the ferrule to a precise position for the new tuned location. After the ferrule is pushed back so that the hub disengages from the angled contact surfaces such as when a connection to another connector occurs, and then the connector is disconnected, the ferrule is then realigned with front housing by the reengagement of the contact surfaces  220 ,  221 ,  222  and the contact regions  214 ,  215 ,  216 .  
         [0039]     The above specification, examples and data provide a complete description of the manufacture and of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.