Abstract:
A fiber optic ferrule receptacle with a single-molded housing having a base, a cylinder on a first side of the base having a bore for receiving an optic ferrule, a socket on a second side of the base, opposing the first side, for receiving an optical element; and the bore having a first diameter at an outer opening distal to the base, and a second diameter at an inner opening adjacent to the base, wherein the first diameter is greater than the second diameter. A second embodiment comprises a single-molded housing having a base, a cylinder on a first side of the base having a bore for receiving an optic ferrule, a socket on a second side of the base, opposing the first side, for receiving an optical element; and a plurality of sloping ridges located on the inner wall of the cylinder, wherein widths of the sloping ridges increase closer to the base.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to receptacles for fiber optic ferrules, and more particularly, the present invention provides a receptacle having improved alignment and mounting capabilities for a fiber optic ferrule. 
     BACKGROUND OF THE INVENTION 
     Referring to FIG. 1, illustrated is a sectional view of an optical module  10  configured in accordance with the prior art. The optical module  10  includes a housing  12  having a cylindrical sleeve  11  with a bore  14 . The housing  12  is constructed of metallic material that can be welded or bonded to a semiconductor element  16 . The semiconductor element  16  has an annular flange  18  and electrical leads  20  extending from a base  22 . The semiconductor element  16  is mounted within a socket  24  of the optical module  10 . The semiconductor element  16  is positioned against the inner walls  26  of the socket by spacers  28 . The semiconductor element  16  is secured within the socket  24  by welding or using an adhesive. 
     The semiconductor element  16  shown in the illustrated embodiment includes a light emitting diode (LED)  30 . In other embodiments the LED  30  can be replaced by a semiconductor laser as a light source. Light waves emitted from the LED  30  are communicated via an optical fiber  32 . An optical ferrule  34  houses and mounts the optical fiber  32  within the bore  14 . An optical fiber terminal  36  positions and mounts the optical fiber cable  38  within the optical ferrule  34 . 
     The diameter of the bore  14  within the cylindrical sleeve  11  is constant. The optical ferrule  34  is inserted and held within the bore  14  resulting in a tight fit within the bore  14 . As a result of the tight fit between the optical ferrule  34  and the bore  14 , misalignment or physical damage to the optical ferrule  34  and/or the bore  14  sometimes results. 
     Semiconductor optical transmitters typically have the design as illustrated in FIG.  1 . Performance of an optical semiconductor transmitter is affected by improper alignment of the transmitter lens or LED  30  with then input end  31  of the optical fiber  32 . Proper alignment maximizes the amount of light from the LED  30  to be focused on the input end  31  of the optical fiber  32 . Conventional techniques for improving this alignment include minimizing the space or gap between the optical ferrule  34  and the bore  14  when the optical ferrule  34  is inserted into the bore  14 . 
     A single-mode optical fiber has a diameter of approximately 10 microns, and the diameter of the bore  14  should match the ferrule  34  diameter on the order of less than several microns in terms of both the tolerance of diameter and circularity. Numerous steps are used in the fabrication process in order to achieve such a high degree of accuracy. Since a conventional housing  12  is made out of metal, very refined mechanical processing is required to fabricate the housing  14 . Moreover, since the diameter of the optical ferrule  34  is typically 2.5 mm, surface roughness must be minimized in order reduce friction and allow insertion or removal of the optical ferrule into or out of the bore in the sleeve. 
     Accordingly, there is a need for an optical ferrule receptacle providing improved alignment of an optical ferrule, which can be produced at an attractive cost. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a receptacle for an optical ferrule having improved alignment capability. 
     Another object of the present invention is to provide an optical ferrule receptacle that can be produced at a reduced cost. 
     A further object of the invention is to provide an optical ferrule receptacle constructed out of a single-molded material, such plastic or other polymer. 
     An additional object of the invention is provide an optical ferrule receptacle having improved socket mounting capabilities for receiving an optical transmitting source. 
     Another object of the invention is to provide an optical ferrule receptacle having improved capabilities for mounting optical ferrules by minimizing damage to the optical ferrule and optical fibers during the insertion process. 
     A further object of the invention is to provide an optical ferrule receptacle having increased assembly speed by facilitating the insertion and securing of the optical ferrule within a an optical bore of the optical ferrule receptacle. 
     Moreover, an object of the present invention is to provide a notch in the housing for a gate where molding material is injected, thereby eliminating the need to remove surrounding excess molding material. The gates are also located in the rear of the receptacle to allow axial flow of molding material during injection molding, thereby producing a symmetric flow around core pins which increases the accuracy of ferrule bore dimensions. 
     According to the present invention, a fiber optic ferrule receptacle is provided having a single-molded housing having a base, a cylinder on a first side of the base having a bore for receiving an optical ferrule, a socket on a second side of the base opposite the first side, for receiving a ball lens, and the bore having a first diameter at an outer opening distal to the base, and a second diameter at an inner opening adjacent to the base, wherein the first diameter is greater than the second diameter. In a second embodiment of the present invention, a single-molded housing is provided having a base, a cylinder on a first side of the base having a bore for receiving an optic ferrule, a socket on a second side of the base, opposing the first side, for receiving an optical element; and a plurality of sloping ridges located on the inner wall of the cylinder, wherein widths of the sloping ridges increase closer to the base. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of an optical ferrule receptacle configured in accordance with the prior art; 
     FIG. 2 is a perspective view of an optical ferrule receptacle and an adjoining cylinder configured in accordance with the present invention; 
     FIG. 3 is a side view of the optical ferrule receptacle and cylinder shown in FIG. 2, wherein the internal configurations are shown in shadow; 
     FIG. 4 is an enlarged side view of the optical ferrule receptacle and cylinder shown in FIG. 3, wherein the optical ferrule receptacle and cylinder are coupled together; 
     FIG. 5 is a perspective view of an optical ferrule receptacle configured in accordance with a second embodiment of the present invention; 
     FIG. 6 is a cross-sectional view of the optical ferrule receptacle shown in and taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is an end view of the optical ferrule receptacle shown in and taken along line  7 — 7  of FIG. 6; and 
     FIG. 8 is a perspective view of the optical ferrule receptacle shown in FIG. 5, wherein the internal configuration is shown in shadow. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 2, illustrated are an optical ferrule receptacle  40  and an adjoining cylinder  42  configured in accordance with the present invention. The optical ferrule receptacle  40  includes a base  44  having a pair of flanges  46 . In a preferred embodiment, the flanges  46  are sloped downward toward the bottom  48  of the base  44 . In other embodiments the flanges  46  may be parallel to the bottom  48  or at different angles. A ferrule sleeve  50  is attached to the bottom  48  of the base  44 . The ferrule sleeve  50  includes a bore  52  (FIG. 3) for receiving an optical ferrule. 
     A socket  54  is attached to the top  56  of the base  44 . The socket  54  is configured for receiving an optical element (not shown), such as a ball lens. The outer periphery of the socket  54  includes an annular groove  58 . The annular groove  58  is sized to fit within an annular ring  60  (FIG. 3) inside the cylinder  42 . The annular groove  58  fits into the annular ring  60  to correctly position and affix the socket  54  inside cylinder  42 . 
     FIG. 3 shows a side view of the optical ferrule receptacle  40  and the cylinder  42  shown in FIG.  2 . The internal configurations of the optical ferrule receptacle  40  and the cylinder  42  are shown in shadow. The ferrule sleeve  50 , ferrule bore  52 , base  44 , and socket  54  are also shown. The cylinder  42  is shown having a socket  52  (in shadow) with an annular ring  60 . The cylinder  42  further includes a socket  64  for receiving a semiconductor module, such as the semiconductor module  16  shown in FIG. 1 having an LED  30  as a light source. It should be noted that a semiconductor laser can be used in place of the LED as the light source, or another light emitting device may be used. In addition to use for a TOSA, the present invention may be applicable for a ROSA assembly also and house a photo detector. 
     In accordance with the present invention, the optical ferrule receptacle  40  is single-molded unit made from a polymer, such as a plastic. Furthermore, the ferrule bore is tapered for one-third the length proximate to the bottom of the base in order to easily, accurately, centrally and securely insert an optical ferrule within the ferrule bore. Moreover, a socket for the lens includes an annular groove on the outer periphery of the socket which is sized to fit within an annular ring of a connecting cylinder to accurately and securely position the socket within the cylinder. 
     The ferrule bore  52  maintains a constant diameter until a transition point  66 . At the transition point  66 , which is about one-third of the total length of the sleeve  50  from the bottom  48  of the base  44 , the diameter of the ferrule bore  52  decreases, preferably, at a linear rate. An aperture  66 , provides a tunnel or pathway connecting the bore  52  with the chamber  70  of the socket  54 . The diameter of the aperture  66  is smaller than the final third portion  75 , thus creating a stop plate  77  against the bottom  48  of the base  44 . Light waves from a light source within the chamber  70 , such as a semiconductor laser or an LED, pass through the aperture  66  and onto a receiving end of an optical fiber mounted within the ferrule bore  52 . The light waves can be focused through the aperture  66  onto an optical fiber by using an optical element, such as a ball lens, located within the chamber  70  of the socket  54 . 
     Since the optical ferrule receptacle  40  is constructed of a polymer, such as plastic, the ferrule sleeve  50  can expand or stretch slightly as an optical ferrule enters the bore  52  and comes in contact with the transition point  66  of the bore  52 . The diameter  72  of the bore  52  at the opening  74  of the sleeve  50  is constant and sized to match, or be only slightly greater, than the diameter of a ferrule being inserted into the bore  52 . The portion  73  of the bore  52  having a constant diameter is preferably two-thirds the overall length of the bore  52 . The portion  73  of the bore  52  functions to accurately position an optical fiber of a ferrule within the bore  52 . 
     At the transition point  66  the diameter of the bore  52  begins to decrease at the final one-third portion  75  of the bore  52 . The decreasing diameter of portion  75  of the bore  52  functions to accurately position an optical fiber within the bore  52 . The decreasing portion  75  also functions to securely mount a ferrule within the bore  52  of the sleeve  50 . The constant diameter  72  of the first portion  73  enables the ferrule to be easily inserted by hand with a zero or low insertion force. The second portion  75  enables the ferrule to be accurately inserted by hand with a low or greater insertion force, resulting in the ferrule being held in place by friction after insertion. 
     The cylinder  42  includes a first socket  62  sized to cover and enclose the socket  54  of the optical ferrule receptacle  40 . The cylinder  42  is preferably constructed of metal and is a single unit. The socket  62  of the cylinder or ring  42  includes an annular ring  62  formed out of the inner wall of the socket  62 . The annular ring  60  is sized to fit into the annular groove  58  of the socket  54 . Since the annular ring  60  is formed out of the inner wall of the cylinder  42 , and thus out of metal, the annular ring  60  will not wear down during a single or multiple couplings with the plastic annular groove  58  of the socket  54 , which is formed from plastic. The socket  62  and annular groove  60  and socket  62  are sized to closely fit around the socket  54 , thus ensuring an accurate positioning and secure fastening during coupling of the receptacle  40  and the cylinder  42 . 
     A second socket  64  of the cylinder  42  is sized to closely fit around and enclose a semiconductor module, such as a semiconductor laser or and LED as shown in FIG. 1. A passage  76  provides an opening that connects socket  62  with socket  64  in the cylinder  42 . The diameter of the passage  76  is smaller than the socket  62 , thus creating and stop plate  79 . The stop plate  79  functions to accurately position the socket  54  during insertion into the socket  62 . Furthermore, the stop plate  79  functions to prevent the socket  54  from twisting and becoming nonparallel to the cylinder  42 . 
     Light waves emitted from a light source module coupled within the socket  64  pass through the passage  76  and into the chamber  70  of socket  54 , which is coupled within socket  62 . The cylinder  42  can be secured to the socket  54  by using an adhesive or by spot welding. Similarly, a semiconductor module can be secured within the second socket  64  by using an adhesive or by spot welding. 
     FIG. 4 illustrates the optical ferrule receptacle  40  and cylinder  42  of FIG. 3 coupled together. In accordance with present invention, the annular ring  60  of the cylinder  42  is positioned within annular groove  58  of the socket  54  of the optical ferrule receptacle  40 . As shown, the socket  54  is correctly positioned within the socket  62  of the cylinder  42 . The annular ring  60  securely holds the socket  54  in the correct location. As such, any adhesive or bonding method is unnecessary. If desired, however, the receptacle  40  and the cylinder  42  may be secured together after coupling. Furthermore, the socket  54  is pressed flat against the stop plate to accurately position and correctly align the socket  54  within the socket  62 . 
     FIG. 5 illustrates another embodiment of the present invention. Shown is an optical ferrule receptacle  80  having a ferrule sleeve  82 , a base  84 , a socket  86 , and an annular groove  88 . The embodiment shown in FIG. 5 includes two notches  90  in the socket  88 . The notches  90  provide a location for the gate  92  wherein molding polymer is injected into a mold for the manufacture of the receptacle  80 . In accordance with the present invention, the gate  92  is located at the notch  92 , thereby eliminating the necessity to scrape or cut off any excess molding material typically associated with a gate for inputting molding material. By locating the gate  92  at the notch  90 , the socket  86  can still be coupled with a closely fitting socket of a corresponding cylinder, without interference from excess molding material surrounding the gate  92 . 
     FIG. 6 is a cross-sectional view of the receptacle  80  shown in and taken along line  6 — 6  of FIG.  5 . FIG. 6 shows a ferrule bore  94  having a consistent diameter  95 . In accordance with a second embodiment of the present invention, the approximate last third of the ferrule bore  94  includes three sloped ridges  97 . In the preferred embodiment, three ridges  97  are contained within the ferrule bore  96  at equally spaced radial locations, or approximately 120 degrees apart. Other embodiments may use more or less sloped ridges  97 . The sloped ridges  97  are preferably part of the same single molded unit of the entire ferrule receptacle  80 . The height of the sloped ridges  97  increases, preferably linearly, beginning at the transition point  96  in the ferrule bore  94 . The height of a sloped ridge  97  is defined as the distance from the inner surface of the ferrule bore  94  to the top of a sloped ridge  97 . The sloped ridges  97  are highest near the base  99 . The surface of the sloped ridges that contact an inserted ferrule may be curved or flat. 
     An optical ferrule is inserted into the ferrule bore  94 . Upon reaching the transition point  96 , the sloped ridges  97  function to firmly grip the optical ferrule and also accurately position the optical ferrule within the optical bore  94 . The sloped ridges  97  also function to prevent an optical ferrule from slipping out of the ferrule bore after the optical ferrule has been inserted. A fully inserted optical ferrule will abut the stop plate  101  located between the aperture  98  and the base  99  of the sloped ridges  97 . 
     An aperture  98  provides a passage between the bore  94  and the chamber  100  of the socket  86 . The annular groove  88  is shown on the periphery of the socket  86 . The notches  90  are shown having gates  92 . 
     FIG. 7 is an end view of the optical ferrule receptacle shown in and taken along line  7 — 7  of FIG.  6 . FIG. 7 shows a view looking into the open end of the ferrule bore  94  of the ferrule sleeve  82 . Illustrated are the sleeve  82  and the three sloped ridges  97 . The aperture  98  and the stop plate  101  can also be seen. 
     FIG. 8 shows an enlarged view of the optical ferrule receptacle  80  shown in FIGS. 5 and 6. The internal construction of the optical ferrule receptacle  80  is shown in shadow. Illustrated are the notches  90  and gates  92  in the socket  86 . An aperture  98  connects the chamber  100  of the socket  86  with the bore  94  of the ferrule sleeve  82 . The sloped ridges  97  are shown to be located between the transition point  96  and the stop plate  101 . Portion  96  of the bore  94  is shown to have a decreasing diameter which begins at transition point  102 . Annular groove  104  is located around the periphery of the socket  86 . The base  84  includes a flange  106 . 
     The description of the foregoing embodiments and operating parameters has been undertaken for the purposes of illustration. The basic principles of the invention can be embodied in other designs or the same design with modifications operating under the same or different conditions without departing from the scope of the invention.