Abstract:
A ferrule has at least one row of optical fiber openings to hold optical fibers. The ferrule also includes a lead-in portion for each of the optical fiber openings to assist in positioning the optical fibers into the optical fiber openings in the ferrule. The optical fiber openings in the ferrule are slightly smaller and have a similar spacing allowing for better fill between the optical fiber openings. A mold core that corresponds to the ferrule is disclosed. The mold core encapsulates at least a portion of the optical fiber opening forming pins, eliminating build up and breakage of the pins.

Description:
[0001]     The present invention relates to a multi-fiber ferrule, and more particularly, a multi-fiber ferrule having at least one row of openings for optical fibers and a lead in portion for each of the openings in the ferrule. The present invention also relates to a mold core that is used to mold the multi-fiber ferrule.  
         [0002]     There are prior art ferrules including, for example, ferrules that have single and multiple rows of optical fiber bores. These ferrules typically have voids in and between the optical fiber bores due to the method used for molding the ferrules. Typically, the pins used to make the optical fiber bores are epoxied together before being inserted into mold. This is a highly labor intensive exercise and presents a risk that the pins will break during removal of the mold core from the mold and or the molded ferrules from the mold. The optical fiber bore forming pins are 250 microns in diameter and when inserted into the mold are spaced with a pitch of 250 microns. This arrangement leads to an inconsistent fill and even large areas of voids, allowing optical fibers to cross over in the optical fiber bores and to be stubbed upon insertion into the ferrule. Additionally, the optical fiber bore forming pins are difficult to replace if one breaks at any point in the process, reducing the productivity of the mold.  
         [0003]     Accordingly, the present invention is directed to an optical ferrule and mold that substantially obviates one or more of the problems and disadvantages in the prior art. Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus and process particularly pointed out in the written description and claims, as well as the appended drawings.  
       SUMMARY OF THE INVENTION  
       [0004]     To achieve these and other advantages and in accordance with the purpose of the invention as embodied and broadly described herein, the invention is directed to a multi-fiber ferrule for securing at least one row of optical fibers, the at least one row of optical fibers comprising at least two optical fibers, the multi-fiber ferrule includes a first row of optical fiber openings, the optical fiber openings having a pitch and each of the optical fiber openings extending from a front face through at least a portion of the ferrule to a first plane, the first plane disposed between the front face and a rear face of the ferrule, and a first stepped portion, the first stepped portion disposed between the first plane and the rear face of the ferrule and having a plurality of grooves, each of the plurality of grooves in communication with a respective one of the optical fibers openings in the first row to provide a lead-in portion for each of the optical fiber openings in the first row, and each of the grooves having a width that is at least 10 microns smaller than the pitch of the optical fiber openings.  
         [0005]     In another aspect, the invention provides for a multi-fiber ferrule for securing at least one row of optical fibers, the at least one row of optical fibers comprising at least two optical fibers, the multi-fiber ferrule includes a first row of optical fiber openings, each of the optical fiber openings extending from a front face through at least a portion of the ferrule to a first plane, the first plane disposed between the front face and a rear face of the ferrule, and a first stepped portion, the first stepped portion disposed between the first plane and the rear face of the ferrule and having a plurality of grooves, each of the plurality of grooves having a width and a depth and being in communication with one of the optical fibers openings in the first row to provide a lead-in portion for the first row of optical fiber openings, and the width of each of the grooves being greater than the depth.  
         [0006]     In yet another aspect, the invention is directed to a mold core used to mold a ferrule that secures at least one row of optical fibers, the mold core includes a main body portion, a plurality of openings extending through the main body portion, a first stepped portion adjacent the main portion, and a plurality of grooves in the stepped portion and in communication with the plurality of openings in the main portion.  
         [0007]     In yet another aspect, the invention is directed to a mold core used to mold a ferrule that secures at least two rows of optical fibers, the mold core includes a main body portion, the main body portion having at least a first stepped portion and a second stepped portion, a plurality of openings extending through the main body, the plurality of openings comprising at least a first plurality of openings and at least a second plurality openings, the first stepped portion encapsulating only a portion of each of openings in the first plurality of openings and the second stepped portion encapsulating only a portion of the openings in the second plurality of openings to provide a lead in portion for each of the plurality of openings in the main body portion.  
         [0008]     In another aspect, the invention is directed to a mold core used to mold a ferrule that secures at least one row of optical fibers, the mold core includes a main body portion, the main body portion including a plurality of openings extending therethrough, a plurality of opening forming pins configured to be disposed in a respective one of each of the plurality of openings, and a reduced portion, the reduced portion being a portion of the main body portion and being configured to encapsulate a portion of each of the plurality of opening forming pins disposed in the openings.  
         [0009]     It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.  
         [0010]     The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification. The drawings illustrate several embodiments of the invention and together with the description serve to explain the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of one embodiment of a ferrule according to the present invention;  
         [0012]      FIG. 2  is a perspective view of the front end of the ferrule in  FIG. 1 ;  
         [0013]      FIG. 3  is a perspective view of a partial cross section of the ferrule of  FIG. 1 ;  
         [0014]      FIG. 3  is a partial perspective view of cross section of the ferrule of  FIG. 1 ;  
         [0015]      FIG. 4   a  is an enlarged perspective view of a cross section of the ferrule of  FIG. 1 ;  
         [0016]      FIG. 4   b  is an enlarged partial cross section view through one of the rows of optical fiber openings of the ferrule of  FIG. 1 ;  
         [0017]      FIG. 5   a  is a partial perspective view of another embodiment of a ferrule according to the present invention;  
         [0018]      FIG. 5   b  is a cross section view of a portion of the ferrule of  FIG. 5   a  along the line  5   b - 5   b;    
         [0019]      FIG. 6   a  perspective view of one embodiment of a mold core according to the present invention;  
         [0020]      FIG. 6   b  is an enlarged view of a portion of the mold core of  FIG. 6   a;    
         [0021]      FIG. 7  is an end view of the mold core of  FIG. 6   a;    
         [0022]      FIG. 8  is the back end view of the mold core of  FIG. 6   a;    
         [0023]      FIG. 9  is a perspective view of another embodiment of a mold core according to the present invention; and  
         [0024]      FIG. 10  is a fiber optic opening forming pin used with the mold cores in the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     A multi-fiber ferrule  10  according to one embodiment of the present invention is illustrated in  FIGS. 1-4   b . The multi-fiber ferrule  10  has a front face  12  and a rear face  14 . The multi-fiber ferrule  10  has at least one row of optical fiber openings  16  extending from the front face  12  toward the rear face  14  and opening into an opening  18  toward the rear of the ferrule  10 . The ferrule  10  also preferably has a window  19  on one of the sides of the ferrule to allow for additional access to the opening  18 . In the embodiment illustrated in  FIGS. 1-4   b , the multi-fiber ferrule  10  has two rows  16 , 16 ′ of optical fiber openings. The optical fiber openings in each of the rows (i.e.,  16   a , 16   b  . . .  16   k , 16   l  of row  16  and  16   a ′ . . .  16   l ′ of row  16 ′) are illustrated as round holes, but could be of any appropriate shape. For example, they could be oval, diamond shaped, v-shaped grooves, or squares.  
         [0026]     The rows of optical fiber openings  16 , 16 ′ open into the opening  18  of the multi-fiber ferrule  10 , as best seen in  FIGS. 3, 4   a  &amp;  4   b . The openings in rows of optical fiber openings  16 , 16 ′ have a pitch P, which is approximately 250 microns. The multi-fiber ferrule  10  also has two stepped portions  20 ,  22  in rear opening  18 . Each of the stepped portions  20 , 22  has a plurality of grooves  24 , 24 ′, and each of the grooves in the plurality of grooves  24 , 24 ′ correspond to one of the openings in the rows of optical fiber openings  16 , 16 ′, respectively. The grooves  24 , 24 ′ act as a lead-in portion for the optical fibers that are to be inserted into the rows of optical fiber openings  16 , 16 ′. The grooves  24 , 24 ′ are preferably wider than they are deep and, as can be seen in  FIG. 4   b , are not as wide as the pitch P, to allow for appropriate ferrule material to fill in between each of the grooves  24 , 24 ′ and the openings  16 , 16 ′ during molding.  
         [0027]     As illustrated in  FIGS. 3, 4   a , and  4   b , each of the optical fiber openings  16   a  . . .  16   l  and  16   a ′ . . .  16   l ′, have two portions, a first portion  26   a  that is in direct communication with a groove  24 , 24 ′ on the stepped portion ( 20 , 22 ), and then a more elongated and more narrow portion  26   b  that extends to the front face  12  and more closely approximates the size of the optical fibers that are mounted in the multi-fiber ferrule  10 . The first portion  26   a  has preferably the same radius (and shape) as the grooves in stepped portions to allow the smooth insertion of the optical fibers (not shown). The optical fiber openings  16 , 16 ′ preferably have a narrowing portion  28  between the first portion  26   a  and the second portion  26   b  to allow the optical fibers to be smoothly inserted into the second portion  26   b  from the first portion  16   a . While the first portion  26   a  in row  16 ′ is longer than the first portion  26   a  for row  16 , they could be the same lengths or reversed in their lengths.  
         [0028]     The first row of optical fiber openings  16  extends from the front face  12  of the ferrule  10  toward the rear face  14  to a plane P 1 . The plane P 1  is positioned between the front face  12  and the rear face  14 . Similarly, the second row of optical fiber openings  16 ′ extends from the front face  12  toward the rear face  14  to a plane P 2 . Plane P 1  is preferably located between the front face  12  and the second plane P 2 . Similarly, plane P 2  is preferably located between plane P 1  and the rear face  14 . Additional rows of optical fiber openings would be similarly disposed relative to one another, with the openings along similarly placed planes.  
         [0029]     The grooves  24 , 24 ′ in the stepped portions  20 , 22  preferably have, as indicated above, the same radius and shape as the fiber optic openings  16 , 16 ′ near the respective plane (P 1 , P 2 ). In the preferred embodiment illustrated in  FIGS. 1-4   b , the grooves  24 , 24 ′ have a generally round configuration that circumscribes less than 180° of a circle. This configuration allows for easy placement of the optical fibers (typically presented into the ferrule  10  in an optical fiber ribbon) into the respective optical fiber openings  16 , 16 ′.  
         [0030]     The rows of fiber optic openings  16 , 16 ′ at the first portion  26   a  are preferably approximately 180 microns in diameter, and are preferably about 2000 microns long along the first portion  26   b . The fiber optic openings  16 , 16 ′ at the second portion  26   b  are preferably about 125 microns in diameter. The individual fiber optic openings as well as the rows of fiber optic openings  16 , 16 ′ preferably have a 250 micron pitch in the ferrule  10 . This pitch, which is consistent with the spacing in the industry, allows for a consistent fill of the ferrule material (typically thermoplastic) along the length of the ferrule  10 , when the diameter of each opening is less than the pitch. It should be noted that since the grooves circumscribe less than 180°, each groove is wider than it is deep. Moreover, since the diameter of each groove is 180 microns and the pitch is 250 microns, there is sufficient space between each groove for the ferrule material to completely fill therebetween.  
         [0031]     While there are two rows  16 , 16 ′ of optical fiber openings illustrated in ferrule  10 , it is contemplated that the ferrule  10  may have only one row of optical fiber openings, more than two rows of optical fiber openings, or any number of rows of optical fiber openings. Furthermore, while 12 openings have been shown in each row of ferrule  10 , there may also be more or fewer openings in each row.  
         [0032]     In an alternative embodiment of a ferrule according to the present invention, a portion of which is illustrated in  FIG. 5 , the ferrule  10 ′ has a plurality of rows of optical fiber openings  30 . As with the above embodiment, the ferrule  10 ′ has a front face  32  and the rows of optical fiber openings extending from the front face  32  toward to the rear of the ferrule. Rather than having stepped portions as in the previous embodiment, the ferrule  10 ′ has a sloped region  34 . The optical fiber openings  30  are illustrated to be round, but may be of any shape, including oval, rectangular, square, or any other appropriate configuration. The fiber optic openings  30  intersect the sloped portion  34  to provide a lead-in portion  36  for inserting the optical fibers into the optical fiber openings  30 . A first row  38  of fiber optic openings  30  extend to a plane P 1 ′ and the lead-in portion  36  corresponding to the fiber optic openings in that row extend from that plane P 1 ′ toward the rear of the ferrule. A second row  40  of fiber optic openings  30  extend to a plane P 2 ′ with the lead-in portion  36  corresponding to that row of fiber optic openings also extends rearwardly. As with the prior embodiment, the lead-in portion  36 , which are grooves as a result of the openings  30  opening into the sloped portion  34 , for the first row  38  of optical fiber openings  30  is between the first plan P 1 ′ and second plane P 2 ′. Similarly, the lead-in portion for the second row  40  of optical fiber openings is between the first plane P 1 ′ and the rear of the ferrule  10 ′.  
         [0033]     One preferred embodiment of a mold core used to form a multi-fiber ferrule is illustrated in  FIGS. 6   a - 8 . The mold core  100  has a main body portion  102  and two stepped portions  104 , 106 . While the illustrated mold core  100  is illustrated with 2 stepped portions, it may have one stepped portion or more than two stepped portions, depending on the number optical fibers to be secured in a multi-fiber ferrule.  
         [0034]     The main body portion  102  has openings  108  extending from a rear face  110  to the front face  112 . The openings  108  also preferably have an enlarged portion  114  around the openings  108  on the rear face  110  to accommodate a shoulder on the fiber optic opening pins, described in more detail below. In the preferred embodiment, the openings  108  are round (cylindrical along their length), but could be of any shape to hold optical fiber opening forming pins that would be appropriate for forming openings that hold the optical fibers as noted above with respect to ferrules  10 , 10 ′.  
         [0035]     The openings  108  open into stepped portions ( 104 , 106 ) at the front face  112  of the main body  102  forming grooves  116 . The grooves  116  are, as extensions of the openings  108 , also generally round in configuration. As can be best seen in  FIG. 7 , the stepped portions extend from the main body, but do not completely encapsulate the entirety of the openings  108 . In fact, as seen in  FIGS. 6   b  and  7 , the stepped portions encapsulate slightly more than half of the openings  108 , or slightly more than 180° degrees of the openings  108  that extend into the stepped portions  104 , 106 . With the fiber optic opening forming pins having more than half of the circumference being encapsulated by the mold core  100 , the fiber optic opening forming pins will not move during injection of the ferrule material into the mold, preventing the material used to form the ferrules (i.e., polymer) from building up between the pins and the mold core. When the ferrule material builds up between the pins the and mold core, causing the pins to move, the lead-in portion ( 24 , 24 ′ of the ferrule  10  described above) of the multi-fiber ferrules may not be coaxial with the optical fiber openings, making insertion loss of the connector higher. Additionally, the fiber optic opening forming pins are less likely to break if they do not move, reducing the costly and time consuming practice of replacing the broken pins.  
         [0036]     As noted above with respect to ferrule  10 , the openings are preferably 180 microns in diameter and have a 250 micron pitch to correspond to the openings in the ferrule. With the increased distance between each of the openings  108  and the resultant openings in ferrule  10 , a better fill is achieved between the rows of openings  16 , 16 ′ in the ferrule, reducing the possibility of optical fibers stubbing or crossing over in the openings.  
         [0037]      FIG. 9  illustrates another embodiment of a mold core  120  according to the present invention. The mold core  120  is similar to the mold core  100 , but has four rows of holes and stepped portions  122 , 124 , 126 , 128  functioning as lead-in portions as described above. The mold core  120  as illustrated has optical fiber opening forming pins  130  inserted into several rows of openings  132 . Again, the rows of openings  132  are the same as described above. One example of the one of the optical fiber opening forming pins  130  is illustrated in  FIG. 10 . The optical fiber opening forming pin  130  has a front portion  132  that forms the opening in the ferrule that opens through the front face (generally corresponds to  26   b  in ferrule  10  in  FIG. 4 ). The front portion  132  is preferably about 125 microns in diameter, generally corresponding to the size of a bare optical fiber that is secured in optical fiber ferrules. The optical fiber opening forming pin  130  also has a back portion  134  that is larger, preferably about 180 microns in diameter, and is used to create the lead-in portions of the ferrule noted above. The optical fiber opening forming pin  130  preferably has a narrowing portion  136  between the front portion  132  and back portion  134 , which corresponds to the narrowing portion  28  in ferrule  10 . An enlarged portion  138  is at the back end of the optical fiber opening forming pin  130  to prevent pin  130  from being pulled through the mold core  120  when the ferrules are removed. While the enlarged portion  138  is illustrated to be a circular member (designed to cooperate with the enlarged portion  114  around the openings  108  on the rear faces of mold cores), it could be of any shape and size to prevent the pins from being pulled through the mold cores. For example, the enlarged portion could simply be a tab, a half circle, an oval, or any other appropriate shape.  
         [0038]     It will be apparent to those skilled in the art that various modifications and variations can be made in the integrated optical module interface of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.