Abstract:
The present invention generally is directed to an optical interconnection sub-assembly, which includes a housing, a longitudinal bore formed through the housing, a tapered ring press-fitted into a first end of the longitudinal bore, a split sleeve ring press-fitted into the tapered ring, a fiber stop press-fitted into the split sleeve ring, and one or more bushings threaded into a second end of the longitudinal bore. The interconnection generally operates to secure a fiber in one end and communicate a signal received from the fiber to a device attached thereto. Further, the interconnection generally does not require any epoxy or other chemical affixation methods, as press fitting and shrink fitting methods are employed, which substantially reduces the assembly time.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the invention generally relate to optical fiber technology, and more specifically, to optical interconnection devices used to connect an optical fiber to an optical device or component. 
   2. Description of the Related Art 
   Optical fibers have generally replaced copper wire as the preferred medium for carrying telecommunications signals. As with copper wire, it is necessary to provide for the interconnection of optical fibers, during installation, repair, or replacement of the fibers, and to terminate the fibers onto active optical devices. Optical devices include, for example, optical switches, optical sensors, and transceivers. The termination of an optical fiber may be indirect, i.e., the fiber may be connected to some other (passive) optical device, such as a beam splitter or polarizer, before the optical signal is directed to the active optical device. The present invention is generally directed to an optical interconnection sub-assembly for a termination of an optical fiber. 
   Optical interconnection sub-assemblies are generally manufactured over a significant period of time as a result of the amount of time it takes to cure the components epoxied inside the sub-assembly. An optical interconnection subassembly generally includes a housing having one or more components therein, such as a fiber stop, ferule-receiving sleeve, or securing bushing. Each component is generally secured to the housing using an epoxy. The securing epoxy takes some time to cure, and consequently, this curing time hinders the manufacturing process of optical interconnection sub-assemblies and reduces the manufacturing throughput. 
   Therefore, a need exists for an easily manufactured, efficient, and cost effective optical interconnection sub-assembly that overcomes the disadvantages of conventional optical interconnection sub-assemblies. 
   SUMMARY OF THE INVENTION 
   Embodiments of the invention are generally directed to an optical interconnection sub-assembly. In one aspect, the optical interconnection sub-assembly includes a housing having a longitudinal bore formed therethrough, a tapered ring secured to a first end of the longitudinal bore, a split sleeve ring secured to the tapered ring, a fiber stop secured to the split sleeve ring, and one or more bushings secured to a second end of the longitudinal bore. Each of the components is generally press-fitted into the housing, and therefore, no epoxy or curing time is required to manufacture the optical interconnection sub-assembly of the invention. 
   Embodiments of the invention further provide an optical interconnection sub-assembly having a first end and a second end. The first end of the optical interconnection sub-assembly is configured for coupling the optical interconnection sub-assembly to an optical device, while the second end of the optical interconnection sub-assembly is configured for receiving a terminal end of an optical fiber. The sub-assembly includes one or more bushings positioned at the second end of the sub-assembly. The bushings are configured for receiving and holding the terminal end of the optical fiber in the sub-assembly. The sub-assembly further includes a split sleeve ring positioned at the first end of the sub-assembly. The split sleeve ring is configured for holding the terminal end of the optical fiber. The split sleeve ring may include a fiber stop secured inside the split sleeve ring. The fiber stop is configured for abutting against the terminal end of the optical fiber. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features of the invention may be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof, which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention, and are therefore, not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments without departing from the true scope thereof. 
       FIG. 1  illustrates a side cross sectional view of an optical interconnection sub-assembly in accordance with an embodiment of the present invention; and 
       FIG. 2  illustrates a perspective view of the split sleeve ring in accordance with an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Embodiments of the invention are generally directed to an optical interconnection sub-assembly. The optical interconnection sub-assembly may be used to connect a terminal end of an optical fiber to an optical device, such as a transceiver or an optical switch, for example. At a front end of the optical interconnection sub-assembly, the optical interconnection sub-assembly is configured to receive the terminal end of the optical fiber. At a back end, the optical interconnection sub-assembly is configured to be connected to an optical device. The optical interconnection sub-assembly generally includes a housing with a longitudinal bore formed through the housing. One or more bushings are placed inside a front end of the longitudinal bore, and a tapered ring is press-fitted inside a back end of the longitudinal bore. A split sleeve ring is press-fitted into the tapered ring, and a fiber stop is press-fitted inside the split sleeve ring. The bushings and the split sleeve ring are generally configured to receive and hold a terminal end of the optical fiber. The split sleeve is configured to hold the fiber stop in addition to the terminal end of the optical fiber. In operation, the bushings and the split sleeve ring hold the terminal end of the optical fiber while the fiber stop abuts against the terminal end of the optical fiber. Generally, the fiber stop is aligned with the terminal end of the optical fiber such that an optical signal transmitted from the terminal end of the optical fiber passes through the fiber stop with minimal connection loss. 
     FIG. 1  illustrates a side cross sectional view of an exemplary optical interconnection sub-assembly  100  of the invention. The optical interconnection subassembly  100  is generally configured to receive a terminal portion of an optical fiber  200  at a front end  110  of the sub-assembly  100 . The back end  120  of optical interconnection sub-assembly  100  is configured to couple to an optical device, such as, an optical switch, a transceiver, and the like. The optical interconnection subassembly  100  generally includes an elongated housing  130  having a longitudinal bore  140  formed therethrough. The longitudinal bore  140  has a front end that coincides with the front end  110  of the sub-assembly  100  and a back end that coincides with the back end  120  of the sub-assembly  100 . The longitudinal bore  140  is generally shaped to hold one or more optical components. For example, the longitudinal bore  140  may be threaded at the front end, cylindrical at the middle, and tapered at the back end. Generally, the longitudinal bore  140  has a diameter of about 1 mm to about 1.25 mm. The housing  130  may be made from a stainless steel material or a heat treated alloy, such as, stainless steel with a condition H 1150 or 430, or Carpenter® custom 718 or 630. In this manner, the housing  130  is generally manufactured from a material that has lesser ductility than the components contained therein. 
   The optical interconnection sub-assembly  100  further includes a first bushing  150  and a second bushing  160  positioned proximate the front end  110 . The first bushing  150  and the second bushing  160  may be positioned inside the optical interconnection sub-assembly  100  by being pressed into the front end of the longitudinal bore  140 . Alternatively, a unitary bushing may be implemented in lieu of the first bushing  150  and the second bushing  160 . Regardless of the number of bushings implemented, the bushings may be double or single threaded, and may be configured to receive and hold the optical fiber  200  therein. More specifically, the inside surface portion  155  of the bushings is generally configured to hold the outer diameter surface  210  of the optical fiber  200 . Additionally, the inner diameter of the bushings may be configured to receive and secure an optical ferrule (not shown) encasing an optical fiber therein. The bushings are generally manufactured from a material that matches the thermal expansion of the housing  130 , such as, materials with a coefficient of thermal expansion (CTE) of 416, 303 or 302 and beryllium copper. However, if two bushings are implemented, embodiments of the invention contemplate that the first bushing  150  may be manufactured from a different material than the second bushing  160 . 
   Furthermore, in order for the respective bushings to be properly secured into the end of housing  130 , the perimeter of exterior surfaces of the respective bushings may have finger members, i.e., members resembling threads without the spiraling pattern associated with threads, extending therefrom. The extending finger members may be used to gauge and regulate the securing force applied to the respective bushings, as the fingers are generally configured to crush or deform at specific forces. These specific crush forces may be correlated with specific securing forces, and therefore, used to regulate the securing force applied to the respective bushings. Factors that may be determinative of the crush force of a particular finger include the physical structure/shape of the finger and the composition thereof, i.e., softer metals may be used to generate lower securing forces, while harder less deformable metals may be used to generate higher securing forces. 
   The optical interconnection sub-assembly  100  further includes a tapered ring  170 , a split sleeve ring  180 , and a fiber stop  190  positioned near the back end  120  of the sub assembly  100 . The tapered ring  170  has an inner surface  172  and an outer surface  174  that is tapered. The inner surface  172  generally defines a cylindrical bore having a uniform diameter. The outer surface  174  generally defines a cylindrical solid having an increasing diameter going from the middle portion of the sub-assembly  100  to the back end  120  of the sub-assembly  100 . The tapered ring  170  is generally press-fitted into the longitudinal bore  140  at the outer surface  174  such that the tapered outer surface  174  slidably engages the longitudinal bore  140  to secure the tapered ring  170  inside the longitudinal bore  140 . That is, the tapered ring  170  is held or secured against the inside portion of the housing  130  primarily by friction. In this manner, no epoxy is required to hold the tapered ring  170  against the inside portion of the housing  130 . In order to facilitate press fitting the tapered ring  170  into the longitudinal bore  140 , the longitudinal bore  140  is generally shaped to receive the tapered ring  170 . For example, the longitudinal bore  140  may be angled so as to facilitate press-fitting the tapered ring  170  into the longitudinal bore  140 . The longitudinal bore  140  may also include an inner ledge  142  and an outer ledge  144 . The inner ledge  142  and the outer ledge  144  are configured to stop the tapered ring  170  from going too far into the longitudinal bore  140 . The tapered ring  170  may be made from a non-heat treated material that is more ductile than the housing  130 , such as copper or steel, for example. As will be made clear in the following paragraphs, the tapered ring  170  is configured to hold the split sleeve ring  180  and the fiber stop  190 . 
   Press-fitted against the inner surface  172  of the tapered ring  170  is the split sleeve ring  180 , which has an inner diameter surface  182  and an outer diameter surface  184 . The split sleeve ring  180  includes a slit, along its length, extending from one end to the other end. In other words, the split sleeve ring  180  includes a longitudinal section that has been removed so as to enable the split sleeve ring  180  to expand and contract according to the size of the component (e.g., fiber stop  190 ) contained inside the split sleeve ring  180 . More particularly, a longitudinal strip is removed from the sleeve ring  180 , which generates a C-shaped solid, as illustrated in FIG.  2 . Once assembled into the sub-assembly  100 , the outer diameter surface  184  is pressed against the inner surface  172  of the tapered ring  170 . This configuration operates to hold the split sleeve ring  180  inside the tapered ring  170  primarily by friction. In this manner, no epoxy is required to hold the split sleeve ring  180  against the inner surface  172  of the tapered ring  170 . The split sleeve ring  180  may also be separated from the second bushing  160  by a distance. In this manner, the split sleeve ring  180  is placed proximate the second bushing  160 . The split sleeve ring  180  may be made from stainless steel, ceramic, beryllium copper, or any material with a proper elastic deformation characteristics, i.e., materials configured to expand to receive the optical fiber  200  therein and then contract to secure the optical fiber  200  inside the split sleeve  180 . The split sleeve ring  180  is configured to hold the fiber stop  190  and the terminal end of the optical fiber  200 . The inside diameter of the split sleeve ring  180  may be slightly less than the outside diameter of the optical fiber  200  to be received therein, so as to accommodate the optical fiber  200  and firmly secure the optical fiber  200  inside the split sleeve ring  180 . 
   A fiber stop  190  is generally press-fitted against the inner diameter surface  182  of the split sleeve ring  180 . The fiber stop  190  has an inner diameter surface  192  and an outer diameter surface  194 , which is press-fitted against the inner diameter surface  182  of the split sleeve ring  180 . The fiber stop  190  is, therefore, held inside the split sleeve ring  180  primarily by friction. In this manner, no epoxy is required to hold or secure the fiber stop  190  against the inner diameter surface  182  of the split sleeve ring  180 . The outer diameter of the fiber stop  190  is generally slightly greater than the inner diameter of the split sleeve ring  180  so as to enable the split sleeve ring  180  to firmly secure the fiber stop  190  therein. The fiber stop  190  (at its front end  196 ) is configured to stop a terminal end of the optical fiber  200 , such that the fiber stop  190  abuts against the terminal end of the optical fiber  200 . The fiber stop  190  further includes a tunnel cavity  220  configured for passing an optical signal transmitted from the terminal end of the optical fiber  200 . The tunnel cavity  220  has a first diameter  197  at the front end  196  of the fiber stop  190  and a second diameter  198  at the back end  199  of the fiber stop  190 , which is significantly larger than the first diameter  197 . The first diameter  197  at the front end  196  is designed to be smaller than the outside diameter of the optical fiber  200  so as to prevent the terminal end of the optical fiber  200  from passing through the fiber stop  190 . The diameter of the tunnel cavity  220  gradually increases from the front end  196  of the fiber stop  190  to the back end  199  of the fiber stop  180  so as to provide an optical clearance for the optical signal transmitted from the optical fiber  200 . The fiber stop  190  is generally aligned with the terminal end of the optical fiber  200 , such that the optical signal from the terminal end of the optical fiber  200  passes through the tunnel cavity  220  with minimal connection loss, thus forming a low loss optical path. The fiber stop  190  may be longitudinally positioned anywhere inside the split sleeve ring  180 . The back end  199  of the fiber stop  190 , however, is generally parallel with the back end of the split sleeve ring  180 , and the length of the fiber stop  190  is generally about half the length of the split sleeve ring  180 . The fiber stop  190  may be manufactured from a material with a low coefficient of thermal expansion, e.g., 416. 
   While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.