Abstract:
The optical connector comprises: a housing portion including: a first bay for engaging a first plug having a waveguide, the first bay being at least partially open at a proximal end and having a wall at a distal end of the first bay; a chamber adjoining the first bay at the wall and having an optical pathway therein; at least two external passive alignment pins integrally formed with the first bay for engaging recesses in the first plug when the first plug is engaged with the first bay; the external passive alignment pins for passively aligning the waveguide to the optical pathway; and an opening in the wall for allowing transmission of an optical signal along the optical pathway between the first plug and the chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application makes reference to the following co-pending U.S. Patent Applications. The first application is U.S. App. Ser. No. 09/281,982, entitled “Fiber Optic Ferrule,” filed Mar. 3, 1999. The second application is U.S. App. Ser. No. 09/323,204, entitled “Electro-Opto-Mechanical Assembly for Coupling a Light Source or Receiver to an Optical Waveguide,” filed Jun. 1, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to connectors for optical fibers, and more specifically for an integral mechanical alignment feature contained therein. 
     2. Description of the Prior Art 
     A typical MT-type connector for an optical multi-fiber cable includes two or more metal pins that engage or plug into housings containing optical and electrical components. Generally the pins are disposed in the plug, outside of the region where the ends of optical fibers are located, and the pins are used to align the ends of the optical fibers with optical components in the housing. 
     Conventionally, the pins for MT-type connectors have been made of metal and are inserted into the connector housing during or after the molding process. However, because the pins and the connector are made of two different materials and are assembled later, it is difficult to maintain the pins in the proper alignment during the manufacturing process. For example, during assembly of a conventional connector great effort must be made to insure that the pins extend the same distance from the connector; and that the pins do not tilt either vertically or horizontally from the connector; and maintaining precise spacing between pins is also an issue. Because the connector and pins may have different thermal expansion coefficients, the pins in the connector may loosen due to thermal cycling of the device. Additionally, the connector must include a considerable region of solid material to provide structural integrity to the anchoring regions for the pins. 
     Therefore, an improved MT-type connector is needed which either reduces or eliminates the difficulties associated with the manufacturing process and thermal cycling of the produced device. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an optical connector in which alignment pins are an integral part of the connector. 
     It is another object of the present invention to provide an optical connector that may be easily manufactured. 
     It is yet another object of the present invention to provide an optical connector in which the alignment of the pins is easily controlled during manufacture. 
     It is yet another object of the present invention to provide an optical connector that does not require additional material fed anchoring alignment pins to the connector. 
     In all of the above embodiments, it is an object to provide a connector that reduces or eliminates thermal expansion effects due to thermal cycling of the device. 
     Finally, it is an object of the invention to provide a simple yet non-obvious pin configuration that takes advantage of the molding process to create a pin integral with the connector. 
     According to one broad aspect of the present invention, there is provided an optical connector comprising: a housing portion including: a first bay for engaging a first plug having a waveguide, the first bay being at least partially open at a proximal end and having a wall at a distal end of the first bay; a chamber adjoining the first bay at the wall and having an optical pathway therein; at least two external passive alignment pins integrally formed with the first bay for engaging recesses in the first plug when the first plug is engaged with the first bay; the external passive alignment pins for passively aligning the waveguide to the optical pathway; and an opening in the wall for allowing transmission of an optical signal along the optical pathway between the first plug and the chamber. 
     According to another broad aspect of the invention, there is provided an optical connector comprising: a housing portion including: a first bay for engaging a first plug having a waveguide, the first bay being at least partially open at a proximal end and having a wall at a distal end of the first bay; a chamber adjoining the first bay at the wall and having an optical pathway therein; at least two external passive alignment pins integrally formed with the first bay for engaging recesses in the first plug when the first plug is engaged with the first bay; the external passive alignment pins for passively aligning the waveguide to said optical pathway; an opening in the wall for allowing transmission of an optical signal along the optical pathway between the first plug and the chamber; and at least two internal passive alignment pins within the chamber for engaging an optical sub-assembly, the internal passive alignment pins for passively aligning an optical axis of the optical sub-assembly with the optical pathway. 
     According to yet another broad aspect of the invention, there is provided an optical connector comprising: a housing portion including: a first bay for engaging a first plug having a waveguide, the first bay being at least partially open at a proximal end and having a wall at a distal end of the first bay; a chamber adjoining the first bay at the wall and having an optical pathway therein; and an opening in the wall for allowing transmission of an optical signal along the optical pathway between the first plug and the chamber, the opening having a first diameter d 1  proximal to the first bay and a second diameter d 2  distal from the first bay, wherein d 1 ≠d 2 , the opening for passively aligning an optical axis of the optical sub-assembly with the optical pathway. 
     Other objects and features of the present invention will be apparent from the following detailed description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in conjunction with the accompanying drawings, in which: 
     FIG. 1A is a partial perspective view from the front side of an optical connector according to the present invention with dashed lines to show interior structures; 
     FIG. 1B is a cross-sectional view of the optical connector of FIG. 1A taken along line I—I; 
     FIG. 2A is a partial perspective view from the rear of an optical connector according to the present invention with dashed lines to show interior structures; and 
     FIG. 2B is a cross-sectional view of the optical connector of FIG. 2A taken along line II—II. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     It is advantageous to define several terms before describing the invention. It should be appreciated that the following definitions are used throughout this application. 
     Definitions 
     Where the definition of terms departs from the commonly used meaning of the term, applicant intends to utilize the definitions provided below, unless specifically indicated. 
     For the purposes of the present invention, the term “uni-body construction” refers to a connector in which the pins and housing portion are formed from one piece of the same material by any process such as, but not limited to: molding pins and housing portions from the same material; etching pins and housing portions from the same material; cutting pins and housing portions from the same material; etc. 
     For the purposes of the present invention, the term “integrally formed pins” refers to alignment pins that are part of a uni-body construction. 
     For the purposes of the present invention, the term “optical pathway” refers to a pathway for light, such as, but not limited to: one or more optical fibers; an optical waveguide; a pathway for light defined by lenses and mirrors; etc. 
     For the purposes of the present invention, the term “OSA” refers to optical sub-assembly. These sub-assemblies include, but are not limited to: optical elements, electro-optic devices, opto-electric devices, mechanical alignment structures, electronic devices, and interconnect means. 
     For the purposes of the present invention, the term “active alignment” refers to a method for aligning two optical elements by activating a light source in one element to detect the output from the second element. The elements are moved in relation to each other to increase the detection of output of light from the second element. 
     For the purposes of the present invention, the term “passive alignment” refers to the alignment of two elements without the activation of a light source in the alignment process. 
     For the purposes of the present invention, the term “recess” refers to a partial or complete hole having any shape and being all or part of the way through an MT-type plug or other device into which a pin of a connector of the present invention extends. 
     For the purposes of the present invention, the term “diameter” as used in conjunction with reference numerals d 1  through d 4  represents the longest linear distance between two points. This term is not intended to imply a circular relationship between elements. 
     Description 
     With reference to the Figures, wherein like references numbers indicate like elements throughout the several views and, in particular, with reference to FIGS. 1A and 1B, an optical connector  100  is illustrated. As may be seen, connector  100  has a housing  102  containing a plug receiving bay  104 . Disposed within plug receiving bay  104  are a pair of passive alignment pins  106  that are integrally mounted to or formed with housing  102  and extend toward a proximal open end of bay  104 . Pins  106  are separated by an internal diameter of d 3 . It should be appreciated that while only two passive alignment pins  106  are illustrated, any number of passive alignment pins  106  may be disposed in communication with housing  102 . In a preferred embodiment, an opening  108  in a proximal end of wall  110  of housing  102  is provided between and in line with pins  106 . Opening  108  allows for communication between a plug containing an external optical pathway and an internal optical pathway within housing  102 . In a preferred embodiment, the plug is a conventional MT-RJ plug (not shown). 
     When the plug is inserted in bay  104 , pins  106  mate with recesses in the plug to align the ends of an external optical pathway with opening  108 . By utilizing passive alignment pins  106 , the external optical pathway is passively aligned with opening  108 . In a preferred embodiment, opening  108  contains an internal optical pathway. 
     FIG. 1B shows a cross sectional view of an optical connector  100  taken along line I—I of FIG.  1 A. As seen in FIG. 1B, opening  108  has two diameters, d 1  adjacent to plug receiving bay  104  and d 2  adjacent to an internal chamber  112 . In a preferred embodiment, diameter d 1  is smaller than diameter d 2  to reduce the amount of RF emission from connector  100 . For a detailed discussion of how to reduce RF emission from these openings, the reader is referred to U.S. App. Ser. No. 09/281,982, entitled “Fiber Optic Ferrule,” filed Mar. 3, 1999. This application is hereby incorporated in its entirety by reference. Additionally, an interior surface  114  of housing  102  is disposed at an angle of Φ. In a preferred embodiment, Φ would be between 0.0° and 90.0°. The addition of interior surface  114  and angle Φ has several advantages over a conventional right angle. These advantages include, but are not limited to: 1) assisting in placing or guiding an optical element into the optical pathways discussed below; 2) reducing diameter d 1  to a minimal amount and also increasing the precision of this diameter; 3) reducing the difficulty of molding housing  102 ; 4) reducing breakage of pins  106  in the molding process; and 5) functioning as a passive alignment feature for aligning optical elements into the optical pathway. 
     The present invention preferably has a uni-body construction to simplify assembly of connector  100 . A uni-body construction also eliminates the need for separate alignment pins that may penetrate too far into housing  102  of connector  100 . Furthermore, because passive alignment pins  106  for plug receiving bay  104  do not extend into internal chamber  112 , space is freed up in internal chamber  112  for mounting larger components in internal chamber  112 . In addition, because the uni-body construction of a preferred embodiment of the present invention allows connector  100  to be molded in one piece, it is easier to control with precision the size, shape, spacing and orientation of passive alignment pins  106 . Once a mold is set-up to produce housing  102  and passive alignment pins  106  of the proper size, shape, spacing and alignment, all connectors  100  produced from that mold will be identical. In contrast, in conventional MT-type connectors where the pins are separate pieces, much greater care must be exercised in manufacturing the connectors to insure that all of the connectors are identical. 
     Turning now to the embodiment illustrated in FIGS. 2A and 2B, an optical connector  200  is illustrated. For clarity, like elements have been provided with like reference numbers except that  100  has been added to each reference number where there is a slight difference in the particular element in this embodiment. The following discussion will focus on the differences between the elements of this embodiment and that of the preferred embodiment. 
     In the second embodiment of the optical connector  200 , housing  202  contains a plug receiving bay  204 . Disposed within plug receiving bay  204  are a pair of passive alignment pins  206  that are integrally mounted to or formed with housing  202  and extend toward a proximal open end of bay  204 . Pins  206  are separated by an internal diameter of d 3 . It should be appreciated that while only two passive alignment pins  206  are illustrated, any number of passive alignment pins  206  may be disposed in communication with housing  202 . In a preferred embodiment, an opening  208  through a wall  210  of housing  202  is provided between and in line with pins  206 . Opening  208  allows for communication between a plug containing an external optical pathway and an internal optical pathway within housing  202 . In a preferred embodiment, the plug is a conventional MT-RJ plug. Elements  202 ,  204 ,  206  and  208  of FIGS. 2A and 2B correspond to elements  102 ,  104 ,  106  and  108  of FIGS. 1A and 1B. These elements have similar functions to those of FIGS. 1A and 1B. 
     As may be seen, two internal passive alignment pins  216  are provided as integral members of housing  202 . As may be seen, internal passive alignment pins  216  project into an internal chamber  212  and are separate by an internal diameter of d 4 . Internal passive alignment pins  216  are used to engage a backplane (not shown). Components on the backplane may include, but are not limited to leadframes, active optical elements such as, but not limited to, lasers; and passive optical elements such as, but not limited to, detectors and lenses. Internal passive alignment pins  216  may be spaced further apart than passive alignment pins  206 . Wider spacing of internal passive alignment pins  216  allows for relatively large optical and electrical components to be disposed between internal passive alignment pins  216  . For example, two pairs of periscope lenses of an optical component may exist in the space between internal passive alignment pins  216 . FIG. 2B illustrates pins  216  as being longer than pins  206 . The relationship between the length of pins  206  and  216  is not drawn to scale. In fact, it is preferable to have pins  216  shorter than pins  206 . 
     FIG. 2B shows a cross sectional view of optical connector  200  taken along line II—II of FIG.  2 A. As seen in FIG. 2B, opening  208  has two diameters, d 1  adjacent to plug receiving bay  204  and d 2  adjacent to internal chamber  212 . In a preferred embodiment, diameter d 1  is smaller than diameter d 2  to reduce the amount of RF emission from the device. For a detailed discussion of how to reduce RF emission from these openings, the reader is referred to U.S. App. Ser. No. 09/281,982, entitled “Fiber Optic Ferrule,” filed Mar. 3, 1999. This application is hereby incorporated in its entirety by reference. Additionally, an interior surface  214  of housing  202  is disposed at an angle of Φ2. In a preferred embodiment, Φ2 would be between 0.0° and 90.0°. Surface  214  has similar functions and advantages of surface  114 . 
     Although passive alignment pins  106 ,  206 , and  216  shown in the drawing Figures have flat tips, the tips of passive alignment pins may be round, angled, or any other suitable shape for engaging the recess in the plug or respective backplane device. The passive alignment pins may extend either partway or entirely through recesses or holes in the plug or respective backplane device. 
     In the embodiments shown in the drawing Figures, the passive alignment pins are shown as being a cylindrical. However, it may be preferred in some circumstances to use pins that are square, rectangular, triangular, oval or other shape in cross section. Also, although only two pins are used to align each plug or backplane components in the embodiments shown in the drawing Figures, it may be desirable to use one or more pins in some circumstances. In an alternative embodiment, no pins are necessary. The preferred number of pins depends on the specific optical component being engaged by the device. 
     While the above embodiments have illustrated the use of alignment pins  106 ,  206  and  216 , it should be appreciated that these pins are optional. By utilizing precision molding in combination with surfaces  114  or  214  one may construct an optical connector  100 ,  200  which does not require passive alignment pins  106 ,  206 , and/or  216 . In this embodiment, interior walls of internal chambers  112 ,  212  would assist in the alignment process. 
     In an alternative embodiment, recesses  222  are designed to engage a mating structure and may replace passive alignment pins  206 . Recesses  222  may also be formed as bumps as illustrated by an element  218 . Similarly, recesses  220  are designed to engage a mating structure disposed on an optical sub assembly. As may be seen, recesses  220  are illustrated as being disposed at the same location as passive alignment pins  216 . This location is merely for illustrative purposes and it should be appreciated that recesses may be disposed anywhere along a proximal wall of chamber  212 . As discussed above, recesses  220  may be replaced by elements  218 . 
     The optical connectors of the present invention may be made of any suitable material conventionally used for waveguide connectors. Preferred materials include glass-filled engineering plastics such as glass-filled polyetherimide. Preferably, all of the pins of the connector are made integrally with the rest of the connector with a conventional method such as molding. 
     The size and shape of the plug receiving bay of the optical connectors will depend on the shape of the plug with which the connector is used. Similarly, the size and shape of the recesses of the plug will determine the size and shape of the passive alignment pins. 
     Although the manufacturing process preferred for the present invention is a unibody construction, the parts of the connector may be formed separately and joined. The housing may be permanently joined or removably connected to a circuit board, backplane, or other suitable substrate. With regard to the second embodiment, it may be preferable to form internal passive alignment pins in conjunction with the backplane device. 
     Although the present invention has been fully described in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, it is to be understood that various changes and modifications may be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.