Patent Abstract:
The present invention provides a ferrule comprising a housing for the stripped end of an optic fiber, and at least one notch and/or protrusion on the outer surface of the ferrule. The present invention further provides a support comprising at least one protrusion and/or groove mating with at least one notch and/or protrusion respectively, on the outer surface of the ferrule for aligning the ferrule and preventing motion (rotational and translational) of the ferrule relative to the support. In various embodiments, the orientation of the optic fiber is fixed with respect to the at least one notch and/or protrusion.

Full Description:
FIELD OF INVENTION 
     The present invention relates to optical fiber connectors. More particularly, the present invention relates to ferrules used in the optical fiber connectors. 
     BACKGROUND OF THE INVENTION 
     Optical fibers find extensive use for transmission of light for digital communications by modulating light signals to convey data or information. The fibers are fragile and have extremely small diameters. Typically, the optical fibers are coupled to a light transmitting device at one end, and light receiving device at the other end. The ends of the fibers may also be coupled in an end-to-end relationship with other mating fibers. In order to provide reliable coupling and ensure high efficiency in the transfer of light or light signals, it is critical that the ends of the optical fibers be precisely aligned with the ends of other fibers or devices to which they are coupled. 
     It is known in the art to use ferrules to provide a mechanically robust mount for holding optical fibers in a desired position. The ferrule is usually a rigid tube that aligns and protects the stripped end of a fiber. Such ferrules are typically made by cutting glass tubes of desired thickness and having a hole at the center, extending through the longitudinal axis of the ferrule. Optical fibers are passed through these holes in the ferrules. 
     The ferrules are held in a housing or support to place them at a desired position and facilitate proper alignment of optical fibers in the connector. Since the optical fibers are very fragile, it is necessary that the ferrule should not rotate, as the rotation of the ferrule would damage the optical fibers extending from the ferrule. Further, translational motion of the ferrule may also cause damage to the optical fibers. Thus, there is a need for a mechanism that addresses the aforesaid concern and ensures that the ferrule is held firmly in the housing or support. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the present invention, a ferrule comprises a housing for the stripped end of an optical fiber and at least one notch on the outer surface of the ferrule suitable for aligning the ferrule and preventing motion (rotational and translational) of the ferrule relative to a support. 
     Another embodiment of the present invention relates to a ferrule and support combination. The ferrule and support combination comprises of a ferrule having a housing for the stripped end of an optic fiber. The ferrule has at least one notch on the outer surface. The support comprises at least one protrusion mating with at least one notch on the outer surface of the ferrule for aligning the ferrule and preventing motion (rotational and translational) of the ferrule relative to the support. 
     According to yet another embodiment of the present invention, a ferrule comprises a housing for the stripped end of an optic fiber, and at least one protrusion on the outer surface of the ferrule suitable for aligning the ferrule and preventing motion (rotational and translational) of the ferrule relative to the support. 
     According to still another embodiment of the present invention, a ferrule and support combination comprises a ferrule comprising a housing for the stripped end of an optic fiber, and at least one protrusion on the outer surface of the ferrule, and a support for aligning the ferrule and preventing motion (rotational and translational) of the ferrule relative to the support. 
     In accordance with yet another embodiment of the present invention, the support further comprises at least one clamp mating with at least one protrusion on the outer surface of the ferrule. In accordance with still another embodiment of the present invention, the support contains a groove mating the protrusion of the ferrule to prevent the ferrule from rotating. Further, the protrusion on the ferrule may be retractable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a ferrule bearing notches in accordance with an embodiment of the present invention. 
         FIG. 2  is an illustration of a portion of a support in accordance with an embodiment of the present invention. 
         FIG. 3  is an illustration of a ferrule-support assembly in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates a ferrule in accordance with another embodiment of the present invention, wherein the ferrule bears protrusions on its outer surface. 
         FIG. 5  is an illustration of a portion of a support in accordance with another embodiment of the present invention. 
         FIG. 6  is an illustration of a ferrule-support assembly in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art will appreciate that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. 
       FIG. 1  illustrates a ferrule bearing notches on its outer surface according to one embodiment of the present invention. The ferrule is a rigid tube usually having a circular cross-section. 
     The ferrule  100  comprises of a housing  102  for seating an optic fiber. The housing  102  is a cylindrical structure having a front-end portion  110 , a central longitudinal bore for receiving an optical fiber therein and a back-end portion  112 . The front-end portion  110  of the ferrule  100  contains at least one hole  108  along the insertion direction of the optical fiber. The back-end portion  112  of the ferrule contains a receptacle to seat the stripped end of the optical fiber. The hole in the front-end portion  110  and the receptacle in the back-end portion  112  of the ferrule are connected through the central longitudinal bore. The stripped end of the optical fiber is inserted in back-end portion  112  in a manner that the stripped portion of the optical fiber passes through the central longitudinal bore to optically couple with hole  108 . The front and back-end portions,  110  &amp;  112  of the ferrule  100 , can be tapered or straight. The precise external shape of the front and back-end portions  110  &amp;  112  of the ferrule and any alignment surfaces will be determined by the need for matching the type of optical fiber connector employed. 
     The ferrule  100  further comprises of two notches  104  and  106  present on the housing  102  of the ferrule  100 . The notches  104  and  106  are used to align the ferrule  100  and prevent motion (rotational and translational) of the ferrule  100  relative to a support (not shown in  FIG. 1 ). The notches  104  and  106  also limit the translational movement of the ferrule  100 . Further, the orientation of the optical fiber with respect to the notches  104  and  106  is fixed. This is useful in applications requiring either a polarizing fiber or polarization maintaining fiber (PMF). The notches  104  and  106  hold ferrule  100  in housing  102  such that the preferred (“fast” or “slow”) axis of the optical fiber lies either perpendicular or parallel to housing  102 . The notches may be conical, square, circular or semi-circular. 
     The ferrule  100  may be made from a ceramic material, however, there are no particular limitations on materials for the ferrule and it can be made from stainless steel, resins, metal, plastic and glass. Further, since an optic fiber end has a domed annular surface, in order to achieve good optical coupling into the optical fiber, the fiber end and the end portions of the ferrule are polished together to sub-micron smoothness. 
     The aforesaid embodiment describes a ferrule with two notches by way of example, without limiting the scope of the present invention. It would be apparent to one skilled in the art that one or more notches may be bored on the surface of the ferrule without deviating from the spirit and scope of the present invention. In an embodiment of the present invention, the notches can be placed on the outer surface and along the axis of the ferrule at regular intervals. In another embodiment of the present invention, the notches can be placed on the outer surface and along circular cross-section of the ferrule at regular intervals. In yet another embodiment of the present invention, the notches can be placed on the outer surface and along the axis of the ferrule at regular intervals. 
       FIG. 2  is an illustration of a portion of a support  200  in accordance with an embodiment of the present invention. Support  200  contains a cavity  202  for holding the ferrule. Support  200  also contains two protrusions  204  and  206 , placed opposite to each other, which extend in the direction of the cavity  202 . The protrusions  204  and  206  fit in the notches of the ferrule  100  to hold the ferrule firmly. In various embodiments, the number of protrusions in the support  200  may correspond with the number of notches in a ferrule. 
     In one embodiment of the present invention, a support may have two flaps, namely, a top and a bottom flap, such that the ferrule is encapsulated within the two flaps. In an alternate embodiment, the support can be a tubular structure with retractable protrusions to facilitate insertion of the ferrule in the cavity. 
       FIG. 3  is an illustration of a ferrule and support assembly  300  in accordance with an embodiment of the present invention. Assembly  300  illustrates ferrule  100  with notches  104  (not shown in Figure) and  106  placed in support  200 . Protrusions  204  (not shown in Figure) and  206  of support  200 , described with respect to  FIG. 2 , fit in the notches  104  and  106 , respectively, of the ferrule  100 . Ferrule  100  is thereby, held firmly in support  200  to prevent motion (rotational and translational) of ferrule  100  relative to support  200 . 
       FIG. 4  illustrates a ferrule  400 , in accordance with yet another embodiment of the present invention, wherein ferrule  400  bears protrusions on its outer surface. Protrusions  404  and  406  present on a housing  402  of ferrule  400  are used to align ferrule  400  and prevent motion (rotational and translational) of ferrule  400  relative to a support in which ferrule  400  is placed. The protrusions  404  and  406  also limit the translational movement of the ferrule  400 . Further, the orientation of the optical fiber with respect to the protrusions  404  and  406  is fixed. This is useful in applications requiring either a polarizing fiber or polarization maintaining fiber (PMF). The protrusions  404  and  406  hold ferrule  400  in housing  402  such that the preferred (“fast” or “slow”) axis of the optical fiber lies either perpendicular or parallel to housing  402 . In different embodiments of the present invention, the shape of protrusions  404  and  406  can be conical, square, circular, semi-circular, or a combination thereof. It would be apparent to one skilled in the art that protrusions of different shapes may be employed without deviating from the spirit and scope of the present invention. 
     The aforesaid embodiment of the present invention describes a ferrule with two protrusions by way of example, without limiting the scope of the present invention. In various embodiments of the present invention, a desirable number of protrusions may be employed including, for example, at least one protrusion. In another embodiment of the present invention, the protrusions can be placed on the outer surface and along the axis of the ferrule at regular intervals. In yet another embodiment of the present invention, the protrusions can be placed on the outer surface and along circular cross-section of the ferrule at regular intervals. 
       FIG. 5  is an illustration of a portion of a support in accordance with an embodiment of the present invention. The support  500  contains a cavity  502  for holding a ferrule. The support  500  also contains two grooves  504  and  506  that are opposite to each other such that the protrusions of the ferrule  400  are seated in the grooves  504  and  506 . In various embodiments, the number of grooves in the support may correspond with the number of protrusions in the ferrule. 
     In one embodiment of the present invention, a support may comprise of two flaps, namely, a top flap and a bottom flap, such that the ferrule is encapsulated within the two flaps. In an alternate embodiment, the support can be a tubular structure, which houses a ferrule having retractable protrusions, to facilitate insertion of the ferrule in the cavity  502  of the support. 
       FIG. 6  is an illustration of a ferrule and support assembly  600  in accordance with an embodiment of the present invention. Assembly  600  illustrates ferrule  400 , with protrusions  404  &amp;  406  on housing  402 , wherein the ferrule is placed in support  500 . When ferrule  400  is placed in support  500 , grooves  504  &amp;  506  of support  500  seat protrusions  404  &amp;  406  of the ferrule, respectively, to hold ferrule  400  firmly in support  500  and thereby prevent motion (rotational and translational) of the ferrule  400  relative to the support  500 . 
     In another embodiment of the present invention, the ferrule may have a combination of notches and protrusions on its surface, with corresponding protrusions and grooves on the support. It would be apparent to one skilled in the art that notches and/or protrusions of various sizes, shapes, and orientations may be employed, without deviating from the spirit and scope of the present invention. Further, a variety of arrangements of the notches and/or grooves on the ferrule surface may be used in various embodiments, as per the desired application. 
     It would further be apparent to one skilled in the art that the present invention is not restricted to ferrules with a circular cross section, but can be used in conjunction with any ferrule that lends itself to rotational or translational motion while it is placed in the support. 
     Although the present invention is described with the reference to the preferred embodiments, however, the scope of the present invention is not limited to the same. It will be appreciated by a person skilled in the art that several other variations of the present invention can exist and fall within the scope of the present invention.

Technology Classification (CPC): 6