Abstract:
A guide insert having a guide member having an arcuate portion for bending an optical fiber of a backplane, and a circuit board assembly comprising the backplane and a daughterboard wherein the daughterboard is operatively connected to the backplane via the guide insert.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser. No. 60/649,455, filed Feb. 2, 2005, the contents of which are hereby expressly incorporated by reference herein in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     Optical fiber as used in standard telecommunications and other applications is based upon the principle of snell&#39;s law and total internal reflection. Each fiber has a central core and an outer layer known as the cladding. By establishing a core with an index of refraction higher than the index of refraction of the cladding, the light will totally reflect internally rather than passing through the core and become lost.  
         [0004]     The employment of a device known as a ferrule makes optical fiber connectors possible. This device supports and aligns the optical fiber or fibers, allowing for a precise coupling of fibers. In a single fiber connector, the ferrule is generally a cylindrical structure, and is often ceramic. The ferrule holds the fiber in a central portion thereof and is adhered therein with cured epoxy resin. Polishing the end of the fiber in the ferrule creates an optically smooth, planar surface with the optical fiber aligned as close as possible to the center of the ferrule. When two unstable ferrules are aligned end to end through a mechanical connector, optical coupling takes place allowing the optical transfer therethrough. However, the joining ferrule surfaces may not be orthogonal, thus producing unwanted reflection.  
         [0005]     Backplanes (circuit boards known in the art as motherboards), which support a plurality of secondary circuit boards (known in the prior art as “daughterboards”) are well known. The daughterboards are connected to the backplane through connectors which not only serve to mechanically grip the daughterboards, but also provide an electrical connection between each daughterboard and the backplane.  
         [0006]     There is a need in the art for an improved optical backplane which permits daughterboards to be optically and electrically connected thereto. It is to such an improved optical backplane and components for constructing the backplane assembly that the present invention is directed.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0007]      FIG. 1  is a perspective view of a circuit board assembly constructed in accordance with the present invention.  
         [0008]      FIG. 2  is a perspective view of an undersurface of the circuit board assembly depicted in  FIG. 1 .  
         [0009]      FIG. 3  is a cross-sectional view of the circuit board assembly depicting a guide insert constructed in accordance with the present invention.  
         [0010]      FIG. 4  is a transverse cross-sectional view of the guide insert shown in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]     Referring now to the drawings, and in particular to  FIG. 1 , shown therein and designated by a reference numeral  10  is a circuit board assembly constructed in accordance with the present invention. The circuit board assembly  10 , in general, comprises a backplane  12 , one or more fiber optic cables  14  ( FIG. 2 ) in the backplane  12 , one or more guide inserts  16  inserted into the backplane  12 , one or more connector assemblies  20  connected to the backplane  12 , (only two of the connector assemblies  20  are numbered in  FIG. 1  for purposes of clarity), and one or more daughterboards  22  attached to the backplane  12  via the connector assemblies  20 . The backplane  12  can be any type of circuit board, such as an electric circuit board, an optical circuit board, or an electro-optical circuit board. In the example depicted in  FIG. 1 , the backplane  12  is designed to support eight daughterboards  22 , but it will be understood by a person of ordinary skill in the art that the backplane  12  may support from one to seven daughterboards  22  or any number above eight which is suitable or appropriate for the particular backplane  12 , used in the invention.  
         [0012]     The backplane  12  has a first side  30 , a second side  32  (shown in  FIG. 2 ), and one or more apertures  34  extending from the first side  30  through to the second side  32  of the backplane  12  (see  FIG. 3 ). As will be described in more detail below, each of the apertures  34  is sized and adapted for receiving one of the guide inserts  16 . In the example shown in  FIG. 1 , the backplane  12  is provided with eight apertures  34  (not shown, each of which containing one of the guide inserts  16 .  
         [0013]     The fiber-optic cable  14  extends across a portion of the second side  32  of the backplane  12 . As shown in  FIG. 2 , preferably the fiber optic cable  12  extends in a serpentine (curved) pattern so as to extend generally adjacent to or across each of the apertures  34  positioned within the circuitboard  12 . The fiber optic cable  14  is a cable constructed of a light transmitting material, such as silica which preferably has a diameter in a range from about 10 micrometers to about 125 micrometers and is surrounded by a cladding. The fiber optic cable  14  described herein may be less than 10 μm in diameter or greater than 125 μm in diameter. Further, it is envisioned that as technology improves the diameter of the light transmitting material within the fiber optic cable  14  will be generally reduced. The fiber optic cable  14  can include more than one cable of light transmitting material or optical fiber. In one embodiment, the fiber optic cable  14  includes a plurality of separate optical fibers (not shown) with each optical fiber adapted to be in communication with at least one of the daughterboards  22  via the guide insert  16  as described herein.  
         [0014]     Each connector assembly  20  is anchored to the backplane  12  in a method known in the art and is in communication with one or more second circuits (not shown but preferably an electrical circuit) residing on the backplane  12 . Typically, the connector assemblies  20  provide electrical connections between the one or more second circuits on the backplane  12  and a circuit on the daughterboard  22 . The connector assemblies  20  may provide electrical connections, optical connections, or electro-optical connections between the backplane  12  and the daughter boards  22 . Connector assemblies, such as the connector assemblies  20  are well known in the art, thus, no further description concerning the construction or use of the connector assemblies  20  is deemed necessary to teach one skilled in the art how to make and use the connector assemblies  20  of the present invention.  
         [0015]     Each of the daughterboards  22  is connected to one or more of the connector assemblies  20  such that the daughterboard circuit of the daughterboard  22  communicates with the one or more second circuits on the backplane  12 . For example, as depicted in  FIG. 1 , each of the daughterboards  22  is connected to the backplane  12  via two connector assemblies  20 . However, it will be understood by a person of ordinary skill in the art that each of the daughterboards  22  may be connected to the backplane  12  by one, two or more connector assemblies  20  depending on the specific requirements of the circuit board assembly  10 .  
         [0016]     Referring now to  FIG. 3 , shown therein is a cross-sectional view of a portion of the circuit board assembly  10 . The guide insert  16  which extends through the backplane  12  functions to support and guide an optical fiber extension  40  of the fiber optic cable  14  (which may comprise a “pigtail” as known in the art, or any extending portion of the fiber optic cable  14 ), for optically connecting the daughterboard  22  with the fiber optic cable  14  in the backplane  12 . In general, the guide insert  16  has a flange  44 , one or more side members  46 , at least one guide member  48 , and a ferrule connector assembly  50 . The flange  44  is connected to the backplane  12  adjacent to the aperture  34  so as to anchor the guide insert  16  to the backplane  12 . As depicted in  FIG. 3 , the backplane  12 , in a preferred embodiment, is provided with a recess  52  extending adjacent to the aperture  34 . The flange  44  is positioned within the recess  52  thereby securing the guide insert  16  to the backplane  12 . The at least one side member  46  is positioned within the aperture  34  so as to extend vertically from the aperture  34 . Preferably the side member  46  extends perpendicularly to the flange  44 , which extends outwardly and laterally from the at least one guide member  48 . Preferably, the guide insert  16  is provided with two side members  46  (see  FIG. 4 ) which are positioned in a parallel orientation and which “sandwich” the at least one guide member  48 . The at least one guide member  48  is thus spaced between the guide members  46 . The guide member  48  has an arcuate portion  56  which extends a distance generally from near the first side  30  of the backplane  12  to near the second side  32  of the backplane  12 . A portion of the optical fiber extension  40  is positioned adjacent to the arcuate portion  56  of the guide member  48  so that the arcuate portion bends the optical fiber extension  40  to a curvature of about 90°. However, the curvature over which the arcuate portion  56  of the guide member  48  bends the optical fiber extension  40  can be varied &gt;90° or &lt;90° so long as the optical fiber extension  40 , of the fiber-optic cable  14  is oriented from the second side  32  of the backplane  12  to the first side  30  of the backplane  12  in any manner suitable for the construction of the circuit board assembly  10 .  
         [0017]     The ferrule connector assembly  50  of the guide insert  16  is positioned adjacent to or extends from a portion of the arcuate portion  56  of the guide member  48 . The ferrule connector assembly  50  supports a ferrule  60  which connects to a terminal position of the optical fiber extension  40  in a manner well known to persons of ordinary skill in the art. The ferrule  60  can be any type of fiber optic ferrule, such as an MT-12 ferrule appropriate and suitable for use in accordance with the present invention. Preferably, the guide insert  16  also has an optional vertical support member  68  positioned between side members  46  and adjacent guide member  48  for supporting the ferrule  60 .  
         [0018]     The guide insert  16  is preferably constructed of an inexpensive material, such as molded thermoplastic material. However, it should be understood that the guide insert  16  can be constructed of any type of material known in the art (e.g., a ceramic) capable of guiding the optical fiber extension  40  and supporting the ferrule  60  connected thereto. In an alternative embodiment, the guide insert  16  is also provided with a second guide member  66  which is similar in construction to the guide member  48 . The second guide member  66  is positioned generally opposite and facing, as in mirror image, to the guide member  48  for guiding the optical fiber extension  40  from a direction generally opposite that provided to guide member  48 .  
         [0019]     The ferrule connector assembly  50 , in one embodiment, is constructed from opposing portions of the guide members  48  and  66  in such a configuration that the guide members  48  and  66  grip the ferrule  60  as shown in  FIG. 3 .  
         [0020]     The circuit board assembly  10  may also comprise a communication link  70 , such as a fiber optic cable, attached to the daughter board  22  for establishing communication between the optical fiber extension  40  and the daughterboard  22 . When the communication link  70  is a fiber optic cable, the communication link  70  is provided with a ferrule  72  connectable to the ferrule  60 . The communication link  70  preferably comprises a connector  74  for connecting the communication link  70  to the daughterboard  22 . The connector  74  can be an optical, electrical or electro-optical connector depending on the type of communication link  70  (e.g., electrical or optical), as well as the type of circuitry on the daughterboard  22  as understood by persons of ordinary skill in the art.  
         [0021]     While the invention is described herein by certain preferred embodiments and examples so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended claims. Thus, the examples provided herein which include preferred embodiments serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the components, structures, operational uses, principles, and conceptual aspects of the invention.  
         [0022]     Changes may be made in the embodiments of the invention described herein, or in parts or elements of the embodiments described herein, or in the sequence of steps of the methods described herein without departing from the spirit and/or scope of the invention as defined in the following claims.