Patent Publication Number: US-2022236495-A1

Title: Fiber optic connector with rear cap

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is being filed on May 21, 2020 as a PCT International Patent Application and claims the benefit of U.S. patent application Ser. No. 62/852,199, filed on May 23, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to terminating the ends of fiber optic cables in fiber optic connectors. 
     BACKGROUND OF THE INVENTION 
     Typically the end of a fiber optic cable is terminated by a fiber optic connector by adhering the fiber within the cable to a ferrule of the connector. Epoxy is commonly used to adhere the fiber to the ferrule. It can be difficult to deliver the epoxy in such a way as to adhere the fiber into the ferrule without also resulting in inadvertently adhering portions of the fiber to other parts of the connector. If a portion of the fiber is inadvertently adhered to the rear part of the ferrule, the fiber would not be free to move and flex based on the direction of pull on the fiber. This lack of freedom of movement can result in failure of the optical fiber. There is a need to provide systems and methods to facilitate the process of connecting the fiber to the ferrule without also inadvertently adhering portions of the fiber to other parts of the connector. 
     SUMMARY 
     The present disclosure provides a system and method for connecting an optical fiber to a ferrule. The system and method facilitate the process of epoxying the optical fiber in a manner that avoid inadvertently adhering the fiber to the side of a connector housing, which can result in breakage of the optical fiber when in the field. The system and method provide a mechanism for easily epoxying the optical fiber to the ferrule while still allowing for radial movement of the optical fiber within the connector housing, which is desirable. The system and method incorporate an end cap that centers the optical fiber in the connector housing during the connection process and also acts as a strain relief when in the field. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of the fiber optic connector of the present disclosure; 
         FIG. 2  is an isometric view of the fiber optic connector of  FIG. 1  partially disassembled; 
         FIGS. 3, 3A and 3B  are longitudinal cross sectional views of the fiber optic connector of  FIG. 1 ; 
         FIG. 4  is a side view of the fiber optic connector of  FIG. 1 ; 
         FIG. 5  is a top view of the fiber optic connector of  FIG. 1 ; 
         FIG. 6  is a front view of the fiber optic connector of  FIG. 1 ; 
         FIG. 7  is a rear view of the fiber optic connector of  FIG. 1 ; 
         FIG. 8  is isometric view of a component of the fiber optic connector of  FIG. 1 ; 
         FIG. 9  is a cross sectional view of the component of  FIG. 8 ; 
         FIG. 10  is isometric view of a component of the fiber optic connector of  FIG. 1 ; and 
         FIG. 11  is a cross sectional view of the component of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the figures, the fiber optic connector and method of the present disclosure are described in further detail. In the depicted embodiment, the fiber optic connector  10  includes a connector housing  12 . The connector housing  12  includes a first end  14  and a second end  16 . The connector housing includes a connector housing axial passage  18  that extends from the first end  14  to the second end  16  of the connector housing  12 . 
     In the depicted embodiment, the axial passage  18  of the connector housing  12  has a circular cross section. In the depicted embodiment, the axial passage  18  is tapered with a smaller diameter portion at the first end  14  of the connector housing and a larger diameter portion at the second end  16 . The second end  16  of the connector housing has an internal diameter D 2 . In the depicted embodiment the connector housing  12  also includes a cantilevered latch  50  that includes a finger nail notch  52  that extend rearward. The cantilevered latch  50  is attached to the first end portion of the connector housing  12 . In the depicted embodiment a finger tab  54  extends rearward from the second end  16  of the connector housing  12  and provides a bump for a finger to engage. The finger tab  54  aids in withdrawing the connector from an adapter (not shown). It should be appreciated that many alternative configurations are also possible. 
     In the depicted embodiment, the connector housing  12  has a single piece construction and is integrally formed. In the depicted embodiment the connector housing  12  is that of an LC style connector. It should be appreciated that the principles of the present disclosure can be applied to a number of other style of connectors including, for example, SC style connectors. 
     The fiber optic connector  10  of the depicted embodiment also includes a ferrule  20 . The ferrule  20  has a first end  22  and a second end  24 . In the depicted embodiment, the second end  24  of the ferrule  20  is secured to the first end  14  of the connector housing  12 . In the depicted embodiment, the ferrule  20  includes a ferrule axial passage  26  that extends from the first end  22  to the second end  24  of the ferrule  20 . 
     In the depicted embodiment the ferrule axial passage  26  has a circular cross section and is sized to receive an end of an optical fiber. In the depicted embodiment, the ferrule axial passage  26  is coaxially arranged with the connector housing axial passage  18 . In the depicted embodiment, the ferrule  20  is axially fixed to the connector housing  12 . In the depicted embodiment, the ferrule  20  is not spring loaded, but can be configured to mate with a spring loaded adjacent ferrule of another connector. In the depicted embodiment, the second end  24  of the ferrule  20  abuts an inner annular shoulder  44  in the connector housing  12 . The first end  22  of the ferrule  20  extend beyond the first end  14  of the connector housing  12 . It should be appreciated that many alternative configurations are also possible. For example, in alternative embodiment the ferrule may be axially movable rather than fixed. 
     The fiber optic connector  10  of the depicted embodiment includes an end cap  28 . The end cap  28  includes a first end  30  and a second end  32 . In the depicted embodiment, the first end  30  of the end cap  28  is secured to the second end  16  of the connector housing  12 . In the depicted embodiment, the end cap  28  has an end cap axial passage  34  that extends from the first end  30  to the second end  32  of the end cap  28 . The end cap axial passage  34  has a circular cross section. The end cap axial passage  34  is coaxially arranged with the connector housing axial passage  18 . It should be appreciated that many alternative configurations are also possible. 
     In the depicted embodiment, the end cap axial passage  34  has an end cap minimum diameter D 1 . In the depicted embodiment, the internal diameter of the axial passage  18  at the second end  16  of the connector housing D 2  is greater than D 1 . In the depicted embodiment, D 1  is at least 40 percent less than D 2 . In the depicted embodiment D 1  is between 0.25 mm and 1.25 mm and D 2  is between 2.0 mm and 3.0 mm. In the depicted embodiment D 1  is between 0.90 mm and 1.10 mm and D 2  is between 2.20 mm and 2.3 mm. The smaller size of D 1  relative to D 2  results in the end cap being able to serve as a centering structure for an optical fiber  48  during the epoxying process. The optical fiber  48  can rest against an edge of the end cap axial passage  34  and be held off of the side surfaces of the second end of the axial passage  18  of the connector housing  12 . This arrangement makes it less likely that any length of the fiber  48  will inadvertently be adhered to the inside surface of the second end of the axial passage  18 . In the depicted embodiment, D 1  is large enough to receive the fiber  48  and still provide enough room to insert a syringe to deliver epoxy to the second end  24  of the ferrule  20 . This allows for the end cap  28  to be secured to the connector housing  12  prior to epoxying the fiber to the ferrule. However, it should be appreciated that the process of epoxying the fiber to the ferrule can occur prior to the end cap  28  being secured to the connector housing  12 . It should be appreciated that many alternative configurations and orders of operations are also possible. 
     In the depicted embodiment, a first end portion  36  of the end cap  28  fits over a cylindrical second end portion  38  of the connector housing  12 , and a second end portion  40  of the end cap  28  extends away from the second end  16  of the connector housing  12 . In the depicted embodiment, the first end  30  of the end cap abuts an annular shoulder  41  on the second end portion  38  of the connector housing  12 . In the depicted embodiment, the second end  16  of the connector housing  12  abuts an annular shoulder  42  in the end cap  28 . In the depicted embodiment, the first end portion  36  of the end cap  28  has a cylindrical inner profile and the second end portion  38  of the connector housing  12  has a cylindrical outer profile. In the depicted embodiment, the end cap  28  is manually slid over the second end portion  38  of the connector housing  12 . In the depicted embodiment, the end cap  28  stretches in this process and is held in place on the connector housing  12  with friction. The cylindrical second end portion  38  of the connector housing  12  has a diameter D 3 . 
     In the depicted embodiment D 3  is between 2.75 mm and 3.30 mm. In the depicted embodiment D 3  is between 2.90 mm and 3.20 mm. The second end portion  40  of the end cap  28  has a length L 1  that is less than the diameter D 3 . In the depicted embodiment L 1  is between 1.0 mm to 3.0 mm. In the depicted embodiment the L 1  is between 1.25 to 1.75 mm. In the depicted embodiment the total length of the end cap (L 1  plus L 2 ) is between 5.00 mm to 6.00 mm. It should be appreciated that many other alternative configurations are also possible. 
     In the depicted embodiment, the end cap  28  is constructed of a resilient material. In the depicted embodiment, the end cap is constructed of TPV (thermoplastic vulcanite) (e.g., Santoprene). In the depicted embodiment, the relative soft construction of the end cap along with its shape and size facilitates its function as a strain relief. It should be appreciated that many alternative configurations and material choices are also possible. 
     In the depicted embodiment, the end cap axial passage  34  in the second end portion  40  of the end cap  28  has a funnel shape having a maximum diameter D 4  at the second end  32  of the end cap  28 . In the depicted embodiment D 4  is between 2.00 mm and 3.00 mm. In the depicted embodiment D 4  is between 2.25 mm and 2.75 mm. In the depicted embodiment, the end cap axial passage  34  has a smooth and continuous transition area from its minimum diameter D 1  to its maximum diameter D 4 . In the depicted embodiment, the axial passage is arranged and configured to provide strain relief for an optical fiber extending through the connector  10 . The transition from D 1  to D 4  forms a curved longitudinal cross-sectional profile. The fiber  48  is supported along that curve when in the field. When the fiber is pulled, it can shift positions towards the direction of pull radially within the end cap  28  and rest against the smooth side of the end cap  28 . The radial movement of the fiber  48  relative to the end cap axial passage  34  on response to the fiber being pulled sideways is desirable. To facilitate the movement, it is desirable that the fiber  48  be connected to the ferrule  20  at its distal end but not glued to the sides of the second end portion of the connector housing axial passage  18 . It should be appreciated that many alternative configurations are also possible. 
     In the depicted embodiment, the fiber optic connector  10  can include the optical fiber  48  including an inner fiber at 125 microns in outer diameter, an outer coating at 250 microns in outer diameter, and a buffer layer at 900 microns in outer diameter. The outer coating is positioned around the inner fiber and the buffer layer is positioned around the outer coating. A first end of the optical fiber is fixed to the ferrule  20  and a second end of the optical fiber extends out of the second ends of the connector housing  12  and end cap  28 . The second end of the optical fiber is free to move radially in the end cap axial passage  34 . It should be appreciated that many alternative configurations are also possible. 
     A method of connecting an optical fiber to a fiber optic connector is also provided. The method includes the step of providing a ferrule  20  fixed to a first end portion  46  of a connector housing  12 . In the depicted embodiment, the method includes the step of connecting an end cap  28  to a second end portion  38  of the connector housing  12 . In the depicted embodiment the end cap  28  has an axial passage  34  with a minimum diameter D 1  that is less than an inner diameter D 2  of a second end  16  of the connector housing  12 . This arrangement facilitates centering of the fiber and minimizes the risk of inadvertently gluing the fiber to the second end portion of the connector housing  12 . The method includes the step of providing epoxy to the ferrule  20 . The method also includes the step of inserting the fiber  48  into the ferrule  20 . The method also includes the step of curing the epoxy. 
     In the depicted embodiment, the step of connecting the end cap  28  to the second end of the connector housing  16  can occur before the step of inserting the fiber into the ferrule. In such an embodiment, the ferrule could be provided with epoxy prior to the end cap  28  being secured or, alternatively, with a syringe after the end cap  28  is secured. Alternatively, the step of connecting the end cap  28  to the second end of the connector housing  12  can occurs after the step of inserting the fiber into the ferrule. In such an embodiment, the end cap could be placed around the fiber at its distal end prior to the distal end being epoxied to the ferrule. The fiber could be inserted into the ferrule before or after the epoxy is provide to the ferrule. The cap configuration and geometry allows for the steps of the method to be performed in a number of different orders. It should be appreciated that many alternative configurations are also possible. 
     The above specification, examples and data provide a complete description of the manufacture and use of the composition 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.