Abstract:
An apparatus that enables a magnification system to view the surface of optical connectors without the need to remove the connectors from a polishing workholder. A connector is placed into a centering insert that is integral to a polishing workholder. The magnification system is fitted with an adapter that engages with the centering insert. This engagement locates the ferrule of the optical connector in the focal plane of the magnification system for viewing and inspection of surface quality.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to a method and to devices enabling the viewing and inspection of the surface quality of optical fiber connectors, and more particularly to an engagement apparatus that permits viewing and inspection while said connectors reside in a polishing workholder.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fiber optic cables are presently used as a transmission media for telecommunication, data communications, video, cable television, sensing systems, power and telemetry. In order to extend cable span lengths, link various fiber segments together, and access terminal equipment such as transmitters and receivers, fiber optic connectors are utilized. Fiber optic connections can be opened and reconnected multiple times providing flexibility for network routing, access and reconfiguration.  
           [0003]    Fiber optic connectors are terminated on the end of an optical fiber. A typical connector consists of a cylindrical ferrule in which an optical fiber is centered and mounted. The connector is secured to the fiber and cable by either adhesive or mechanical gripping means.  
           [0004]    The final step in the termination of a fiber optic connector is the polishing of the fiber end face. The terminated connector is placed into a polishing workholder. Typically, the workholder is a jig device shaped like a disk. When inserted into the workholder, a small portion of the connector ferrule extends beyond the bottom workholder surface. The workholder is precisely machined to hold the connector either perpendicular or at a predetermined angle in reference to a polishing platen.  
           [0005]    Abrasive polishing films are placed on the platen. As the workholder repetitively moves the ferrule across the film, fiber surface material is removed. Several types of films, varying in the degree of abrasiveness, may be used in the process. The end desired result is a smooth, scratch and defect-free fiber surface finish. This procedure results in a low loss and high performing connector.  
           [0006]    In order to insure a correct fiber finish, the connector end face needs to be inspected. A microscope usually accomplishes this task. Suitable microscopes include manual units with eyepieces for direct viewing and video devices for viewing the magnified connector image on a monitor.  
           [0007]    Prior art demonstrates adapters on microscopes that permit stand-alone connectors to be individually inserted into the microscope. This necessitates the removal of the connector from the workholder before inspection and reinsertion after inspection if additional polishing is required. This excessive material handling is time consuming. Labor rates are a large contributor to overall connector termination costs. This is not acceptable in the very cost sensitive connector industry.  
           [0008]    The excessive material handling of prior art is compound with the introduction of automated mass polishing units that have workholders capable of holding and polishing from 12 to 48 connectors simultaneously. Each one of these connectors needs to be removed from the workholder, one-by-one, for individual inspection.  
           [0009]    A significant shortcoming of prior art is that the required excessive material handling increases the possibility of particle contamination and potential damage to the fiber surface.  
           [0010]    The introduction of new connector types and performance specifications requires the development of advanced polishing techniques and procedures. This research involves intensive testing involving different polishing speeds, polishing pressure and abrasive films. Constant microscopic inspection is required during all stages of this development process. Prior art makes this tedious because of the need to remove and reinsert connectors into and out of workholder and microscope.  
           [0011]    Many types of optical connector styles are offered in the marketplace. These styles differ in connector hardware and ferrule sizes. Prior art requires a microscope to have different adapters for each type of connector to be inspected. This necessitates the continual changing of adapters in order for the microscope to accept connectors for viewing.  
         SUMMARY OF THE INVENTION  
         [0012]    Therefore, it is the object of the invention to provide a convenient means for viewing the end faces of optical fiber connectors without removing them from a polishing workholder.  
           [0013]    An advantage of the present invention is to provide an engagement system between a polishing workholder and a viewing microscope. This engagement will align the connector end face with the focal plane of the microscope.  
           [0014]    Still another advantage of the present invention is that the said engagement does not rely upon the connector type or ferrule size and shape. The engagement mechanism is integral to the workholder and microscope interface.  
           [0015]    A further advantage of the present invention is that it vastly decreases material handling since it does not require a connector to be removed from the polishing workholder in order to inspect its end face with a microscope instrument.  
           [0016]    An additional advantage of the present invention is that the resulting decrease in material handling significantly reduces possible connector contamination and damage.  
           [0017]    It is still another advantage that the present invention does not require a multitude of individual connector adapters to be interchanged on a microscope in order to view varying styles of connector types and ferrule sizes.  
           [0018]    The present invention also has the advantage of minimizing the amount of microscope focus adjustment since the engagement mechanism automatically aligns the connector end face with the microscope focal plane.  
           [0019]    An advantage of the present invention is that the engagement mechanism does not make physical contact with the optic connector. The only contact is between the microscope and the workholder. This minimizes potential connector damage and contamination.  
           [0020]    Other advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    For a more complete understanding of this invention reference should now be had to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0022]    [0022]FIG. 1 is an isometric view of the preferred embodiment&#39;s centering means.  
         [0023]    [0023]FIG. 2 is a cross sectional view of centering means with an optical connector inserted.  
         [0024]    [0024]FIG. 3A is an isometric view of centering means mounted within a polishing workholder.  
         [0025]    [0025]FIG. 3B is a cross sectional view of centering means mounted within a polishing workholder.  
         [0026]    [0026]FIG. 4A is an isometric view of the embodiment&#39;s adapter means.  
         [0027]    [0027]FIG. 4B is a cross sectional view the adapter means.  
         [0028]    [0028]FIG. 5 is a cross sectional view of the adapter means engaged with an optical magnification means.  
         [0029]    [0029]FIG. 6 is a cross sectional view of the embodiment illustrating the engagement between the centering means and adapter means.  
         [0030]    [0030]FIG. 7 is an isometric view of another embodiment of the present invention illustrating a centering means mounting in a polishing workholder.  
         [0031]    [0031]FIG. 8 is cross sectional view of the embodiment of FIG. 7 illustrating the engagement between the adapter means and the optical magnification means.  
         [0032]    [0032]FIG. 9 is a cross sectional view of the embodiment of FIG. 7 illustrating the engagement between the centering means and adapter means.  
         [0033]    [0033]FIG. 10 is an isometric view of another embodiment of the present invention illustrating the locating means of the polishing workholder.  
         [0034]    [0034]FIG. 11 is a cross sectional view of the embodiment of FIG. 10 illustrating the adapter means engaged with an optical magnification means.  
         [0035]    [0035]FIG. 12 is cross sectional view of the embodiment of FIG. 10 illustrating the engagement between the adapter means and the locating means. 
     
    
       [0036]    While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]    Referring to FIG. 1, apparatus  1  is provided with a centering means  20 . Centering means  20  is tubular in shape. Suitable tubular cross-sections include circular, elliptical, square and rectangular. Circular is preferred. Suitable materials for centering means  20  include stainless steal, aluminum and brass. Stainless steel is preferred. Center means  20  is provided with a closed end  22  and an open end  24 . Closed end  22  is provided with a chamfer  26 . Closed end  22  is also provided with a through hole  28 . Through hole  28  is aligned with the center axis of centering means  20 .  
         [0038]    Referring next to FIG. 2, through hole  28  has a diameter large enough to accept a ferrule  30  of an optical connector  32 . The inner diameter of center means  20  is large enough to accept the insertion of connector  32 . When connector  32  is inserted into centering means  20 , ferrule  30  protrudes beyond the surface of closed end  22 .  
         [0039]    Referring now to FIG. 3A, a polishing workholder  34  is illustrated. Suitable polishing workholders include those manufactured by Krell Technologies, Englishtown, N.J., having part numbers SM3-10 and SP3-10. Polishing workholder  34  is provided with a plurality of through holes  36 . Centering means  20  are inserted and mounted in through holes  36 . Mounting means include press-fitting and epoxy. As illustrated in FIG. 3B, centering means  20  is positioned so that the bottom of chamfer  26  is above the surface of polishing workholder  34 .  
         [0040]    An adapter means  38  is illustrated in FIG. 4A. Adapter means  38  has the same tubular shape as centering means  20 . Suitable materials for adapter means  38  are stainless steel, aluminum, brass and polymer plastics. Stainless steel is preferred. The inner diameter of adapter means  38  is large enough to accept the outer diameter of centering means  20 . A slip fitting between adapter means  38  and centering means  20  is preferred. One end of adapter means  38  has internal threading as shown in FIG. 4B.  
         [0041]    Referring to FIG. 5, an optical magnification means  42  is illustrated. Suitable optical magnification means include microscopes, fiberscopes, borescopes and video inspection systems. The SpecVision Video Inspection System manufactured by Krell Technologies, Inc., Englishtown, N.J., having a part number SV3 is preferred. Magnification means  42  is provided with an objective  44  attached at a base  46 . Base  46  has an external threading  48  which permits engagement with the internal threading  40  of adapter means  38 . Adapter means  38  is of sufficient length, that when attached to base  46  through the engagement of threading  40  and threading  48 , the focal plane  50  of objective  44  lies within adapter means  38 . When attached to base  46 , the center axis of adapter means  38  coincides with the optical train axis  52  of magnification means  42 .  
         [0042]    The operation of apparatus  1  will now be described. Referring to FIG. 6, adapter means  38  is threaded onto base  46  of magnification means  42 . Optical connector  32  is inserted into centering means  20  so that ferrule  30  protrudes above the surface of closed end  22 .  
         [0043]    Adapter means  38  is slipped over centering means  20  until it bottoms out against the surface of polishing workholder  34 . Upon contact between adapter means  38  and polishing workholder  34 , the axis of ferrule  30  is aligned with optical train axis  52 . Additionally, the front surface of ferrule  30  is aligned with focal plane  50  of objective  44 . This alignment permits the front surface of ferrule  30  to be viewed by optical magnification means  42 .  
         [0044]    In another embodiment of the present invention, apparatus  2  of FIG. 7 is shown with polishing workholder  34  formed with a plurality of grooves  54  on its front surface. Centering means  20  are located in the center of grooves  54 .  
         [0045]    Referring now to FIG. 8 an adapter means  38 A and optical magnifications means  42  are illustrated. Adapter means  38 A is tubular in shape and its cross sectional dimensions match that of groove  54 . Suitable materials for adapter means  38 A are stainless steel, aluminum, brass and polymer plastics. Stainless steel is preferred. One end of adapter means  38 A has internal threading  40 A that permits engagement with base  46  of magnification means  42 . Adapter means  38 A is of sufficient length, that when attached to base  46 , the focal plane  50  of objective  44  lies within adapter means  38 A. When attached to base  46 , the center axis of adapter  38 A coincides with the optical train axis  52  of magnification means  42 .  
         [0046]    The operation of apparatus  2  will now be described. Referring to FIG. 9, adapter means  38 A is threaded onto base  46  of magnifications means  42 . Optical connector  32  is inserted into centering means  20  so that ferrule  30  protrudes above the surface of closed end  22 .  
         [0047]    Adapter means  38 A is pressed into groove  54  until it bottoms out. Upon contact between adapter means  38 A and polishing workholder  34 , the axis of ferrule  30  is aligned with optical train axis  52 . Additionally, the front surface of ferrule  30  is aligned with the focal plane  50  of objective  44 . This alignment permits the front surface of ferrule  30  to be viewed by optical magnification means  42 .  
         [0048]    In still another embodiment of the present invention, apparatus  3  of FIG. 10 illustrates an optical connector  32  mounted in a polishing workholder  34 B. A ferrule  30  of optical connector  32  protrudes above the bottom surface of workholder  34 B. Ferrule  30  has a center axis  60 . Workholder  34 B has a locating means  58  consisting of the workholder surface area that is surrounding protruding ferrule  30 .  
         [0049]    [0049]FIG. 11 illustrates an adapter means  38 B attached to an optical magnification system  42 . Adapter means  38 B is tubular in shape and open at both ends. Suitable materials for adapter means  38 B are stainless steel, aluminum, brass and polymer plastics. Stainless steel is preferred. One end of adapter means  38 B has an internal threading  40 B that permits attachment to a base  46  of optical magnification system  42 . Adapter means  38 B is of sufficient length that when attached to base  46 , the focal plane  50  of objective  44  lies within adapter means  38 B. Optical magnification system  42  has an optical train axis  52 . The other end of adapter means  38 B has an inner perimeter larger than the outer perimeter of a ferrule  30 .  
         [0050]    The operation of apparatus  3  will now be described. Referring to FIG. 12, adapter means  38 B is threaded onto base  46  of optical magnification system  42 . Optical connector  32  is inserted into polishing workholder  34 B until ferrule  30  protrudes above the bottom surface of workholder  34 B.  
         [0051]    The other end of adapter means  38 B is placed over ferrule  30  until it bottoms out against locating means  58 . Upon engagement between adapter means  38 B and locating means  58 , the front surface of ferrule  30  is aligned with the focal plane  50  of objective  44 . Adapter means  38 B is then laterally moved about locating means  58  to align the center axis  60  of ferrule  30  with the optical train axis  52  of optical magnification system  42 .