Abstract:
A pigtail-less optical connector assembly is described that is capable of data rates as high as 10 GHz. The described optical connector assembly connects the optical fiber connector to an optical die element mounted in the connector assembly using optical fiber ribbon and an optical deflecting device. The optical fiber connector is slideable within the connector assembly and is resiliently biased toward a home position. The connector assembly is designed to allow the optical fiber ribbon to flex without damaging the fiber ribbon as the optical fiber connector slides.

Description:
FIELD 
     This disclosure relates to a pigtail-less optical connector assembly having one or more integrated optical die elements, such as optical transmitter die(s), optical receiver die(s), or optical transceiver die(s), integrated therein. The described optical connector assembly is suitable for 10 GHz data transmission and receiving rates. 
     BACKGROUND 
     Pigtail-less optical connector assemblies are known from U.S. Pat. Nos. 7,854,554 and 7,905,664. The optical connector assemblies described in these patents have data rates that are limited by a number of factors, including by the electrical flex circuits that are used. However, higher data rates than those provided by these known optical connector assemblies are desirable. 
     SUMMARY 
     A pigtail-less optical connector assembly is described that is capable of data transmission and receiving rates (hereinafter referred to simply as “data rate”) as high as 10 GHz (10 Gbit/s). One or more of the described optical connector assemblies can be mounted adjacent to an edge of a circuit card for providing optical connection between the circuit card and an optical backplane. 
     The described optical connector assembly connects the optical fiber connector to an optical die element mounted in the connector assembly using optical fiber ribbon and an optical deflecting device. The optical fiber connector is slideable within the connector assembly and is resiliently biased toward a home position. The connector assembly is designed to allow the optical fiber ribbon to flex without damaging the fiber ribbon as the optical fiber connector slides. 
     In one embodiment, the connector assembly includes a housing structure having a first end and a second end. An optical fiber connector is adjacent to the first end of the housing structure and is at least partially disposed in the housing structure. The optical fiber connector is exposed outside the housing structure to permit establishment of an optical connection between the connector assembly and an optical connector on an optical backplane. A biasing mechanism is at least partially disposed within the housing structure and acts on the optical fiber connector to bias the optical fiber connector toward the first end. An electrical connector is adjacent to the second end of the housing structure and is at least partially disposed in the housing structure. The electrical connector is exposed outside the housing structure to permit establishment of an electrical connection between the connector assembly and a circuit card on which the connector assembly is to be mounted on. A circuit board is disposed within the housing structure, with the circuit board including at least one optical die element and driver circuitry for the optical die element disposed thereon. Electric circuitry connects the driver circuitry and the electrical connector. An optical deflecting device is disposed within the housing structure adjacent to the optical die element for deflecting an optical path to and from the optical die element. In addition, an optical fiber ribbon is disposed within the housing structure and has a first end that is optically connected to the optical fiber connector and a second end that is optically connected to the optical deflecting device. 
     In another embodiment, a circuit card assembly is formed by a circuit card with electronic components mounted thereon, and one or more of the described connector assemblies mounted on the circuit card adjacent to an edge thereof with the electrical connector electrically connected to the electronic components. 
    
    
     
       DRAWINGS 
         FIG. 1  illustrates a circuit card assembly including an optical connector assembly described herein mounted adjacent the edge of a circuit card. 
         FIG. 2  is a perspective view of the optical connector assembly. 
         FIG. 3  is an exploded view of the components of the optical connector assembly. 
         FIG. 4  is a longitudinal cross-sectional view taken along line  4 - 4  of  FIG. 2 . 
         FIG. 5  is a perspective view of a portion of the optical connector assembly to illustrate the interaction between the optical fiber ribbon and the block of the biasing mechanism. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a circuit card assembly  10  that includes a circuit card  12  and an optical connector assembly  14  mounted on the circuit card  12 . As is conventional, the circuit card  12  includes a plurality of electronic components (not shown) mounted thereon for performing the design function of the circuit card. The electronic components can be laid out in any desired arrangement and can perform any desired function(s) known to those of skill in the art. 
     The connector assembly  14  is disposed adjacent to an edge, for example the rear edge, of the circuit card  12  so that the connector assembly  14  can optically connect with a suitable optical connector assembly on an optical backplane (not shown) of conventional construction. The circuit card  12  includes a mounting area  16  adjacent to the edge that is configured for receiving the connector assembly  14 . In the illustrated embodiment, the mounting area  16  is configured for receiving up to six of the connector assemblies  14 , three of the assemblies  14  on the front or visible side (i.e. visible in  FIG. 1 ) of the circuit card  12  and three of the assemblies on the rear or non-visible side of the circuit card  12 . So although only a single connector assembly  14  is illustrated in  FIG. 1 , a plurality of the connector assemblies  14  can be mounted on the circuit card. As seen in  FIG. 1 , the circuit card assembly  10  includes six ports  18 , one for each of the connector assemblies, which ports  18  facilitate connection to the connector assemblies on the backplane. 
     Turning now to  FIGS. 2-5 , the connector assembly  14  will now be described in detail. As described herein, the connector assembly  14  is configured for up to an approximately 10 GHz data rate. 
     The connector assembly  14  includes a housing structure  20  having a first end  22  and a second end  24 . In the illustrated example, the housing structure  20  is formed by three primary components, namely a first package body  26 , a second package body  28  and a cover  30 . The package body  26  and the package body  28  are formed with a snap fit connection mechanism to connect the package body  26  and the package body  28  together, and formed with open tops that are closed off and covered by the cover  30 . In one embodiment, the cover  30  is formed of a material to provide high thermal conductivity, while the package bodies  26 ,  28  are formed of plastic material that provides electro-static dissipative (ESD) protection. 
     With reference to  FIGS. 3 and 4 , the first package body  26  is a generally hollow structure having an opening  32  at one end thereof through which an optical fiber connector (discussed further below) extends. The opposite end of the package body  26  is substantially open. The interior of the package body  26  defines a lower cavity or open region  34  that receives the optical fiber connector and a biasing mechanism (discussed further below), and an upper cavity or open region  36  that receives other components discussed further below. The outside of the package body  26  is formed with opposite channels  38  with detents  40  at the ends of the channels (only one channel and detent is visible in  FIG. 3 ). 
     With reference to  FIGS. 2-4 , the second package body  28  comprises a horizontal shelf structure  42  having an opening  44  formed therethrough. A vertical wall  46  extends downwardly from the front of the shelf structure  42 , and a pair of spaced arms  48   a ,  48   b  extend from the wall  46  in a direction toward the first end  22 . The arms  48   a ,  48   b  each include a detent  50  at the distal end thereof. In use, the arms  48   a ,  48   b , channels  38 , and the detents  40 ,  50  form a snap fit connection to connect the package body  26  and the package body  28 . As shown in  FIG. 2 , the arms  48   a ,  48   b  slide in the channels  38  on either side of the package body  26  until the detents  50  snap fit behind the detents  40 , thereby locking the package bodies together. 
     Each of the arms  48   a ,  48   b  also includes a locating protrusion  52  extending downwardly therefrom. The location protrusions  52  are positioned and configured to fit into locating holes  53  formed in the mounting area  16  of the circuit card  12  for positioning the connector assembly. In addition, as best seen in  FIGS. 3 and 4 , the vertical wall  46  includes a spring detent protrusion  54  around which an end of a biasing spring is disposed for fixing the end of the spring. 
     In addition, with reference to  FIG. 5 , the interior of the horizontal shelf structure  42  is provided with a plurality of ledges  56  (only one ledge is visible in the figures) that in use supports a circuit board of the connector assembly. Similar ledges (not visible) are formed in the upper cavity  36  of the first package body  26  for supporting the circuit board. 
     Turning to  FIGS. 2-5 , an optical fiber connector  60  is adjacent to the first end  22  of the housing structure  20  and is at least partially disposed in the housing structure. In particular, an end of the fiber connector  60  extends through the opening  32  and into the port  18  to expose the end outside the housing structure to permit establishment of an optical connection with the connector assembly  10 , while an opposite end  62  of the connector  60  is enlarged to retain the end  62  in the lower cavity  34  of the first package body  26 . 
     The optical fiber connector  60  can be any type of optical fiber connector suitable for establishing optical connections with the connector assembly  10 . For example, in the illustrated embodiment, the optical fiber connector  60  is a mechanical transfer (MT) connector having connector pins  64  and exposed ends  66  of optical fibers. The construction and operation of optical fiber connectors, including MT connectors, is well known in the art. 
     With reference to  FIGS. 3-5 , a biasing mechanism  70  is at least partially, and in the illustrated embodiment completely, disposed within the housing structure  20 . In particular, the biasing mechanism  70  is disposed in the lower cavity  34 . The biasing mechanism  70  acts on the optical fiber connector  60  to bias the optical fiber connector toward the first end  22 . Any form of biasing mechanism that achieves the biasing effect can be used. In the illustrated example, the biasing mechanism  70  comprises a block  72  that abuts against the end  62  of the connector  60 , and that extends rearward in the lower cavity  34  to a rear end. A coil spring  74  disposed in the lower cavity  34  is disposed between the rear end of the block  72  and the vertical wall  46  for applying the biasing force. A spring detent protrusion  76  is provided on the rear end of the block  72  around which the second end of the spring  74  is disposed for fixing the second end of the spring. Although a coil spring has been described as being used to apply the biasing force, other mechanisms capable of applying a biasing force can be used. 
     A circuit board  80  is disposed within the housing structure  20 . In the illustrated embodiment, the circuit board  80  is oriented in a generally horizontal plane and extends longitudinally with a first portion disposed within and supported by the horizontal shelf structure  42  and a second portion supported by the first package body  26  and disposed within the upper cavity  36 . 
     The first portion of the circuit board  80  includes an electrical connector  82  mounted thereon so as to position the electrical connector  82  adjacent to the second end  24 . The electrical connector  82  is mounted on the downward facing surface of the circuit board  80  at a location corresponding to the opening  44 . The opening  44  exposes the electrical connector outside the housing structure  20  to permit establishment of an electrical connection between the assembly  14  and the circuit card  12 . Although the electrical connector  82  is described and illustrated as being mounted on the board  80 , the connector  82  could be separate from, but electrically connected to, the board  80 , for example by being mounted on a circuit board that is separate from the circuit board  80 . 
     The electrical connection can be any high speed electrical connection that one finds suitable for use with the connector assembly  14 . In the illustrated example, the electrical connector  82  includes a pin array  84  that extends down from the electrical connector and through the opening  44  for electrical connection to a mating connector on the circuit card. Alternatively, Fuzz Button® technology available from Custom Interconnects, LLC of Centennial, Colo. could also be used as the electrical connector. A pair of locating pins  86  also extend downwardly from the electrical connector  82  for installation within locating holes  88  (seen in  FIG. 1 ) in the circuit card in the mounting area  16  to help properly position the connector assembly  14  on the circuit card. 
     The circuit board  80  also includes at least one optical die element suitable for transmitting and/or receiving optical signals and driver circuitry for the optical die element mounted thereon. In the illustrated embodiment, the optical die element and driver circuitry are part of a micro-electronic optical core  90  that is available from Ultra Communications, Inc. of Vista, Calif. 
     In one embodiment, the optical core  90  includes both a transmitter die and a receiver die, as well as driver circuitry for each. The transmitter die can be any device configured to transmit optical signals. For example, the transmitter die can be a vertical cavity surface emitting laser (VCSEL) array die. The receiver die can be any device configured to receive optical signals. For example, the receiver die can be a pin diode array (PDA). The driver circuitry is configured to convert optical signals into electrical signals in the case of receiver die driver circuitry, or convert electrical signals into optical signals for transmission by the transmitter die in the case of transmitter die drive circuitry. The function and operation of transmitter and receiver die and their driver circuitry is known to those of ordinary skill in the art. 
     Other combinations and numbers of dies can be employed on the core  90 . For example, a single die that performs both transmit and receive functions (i.e. a transceiver die) could be used. In addition, two or more transmitter dies, or two or more receiver dies, or two or more transceiver dies, or any combination thereof, could be employed. The number of die and the function of the die depend at least in part on the intended function(s) of the connector assembly  14 . 
     The optical core  90  can be mounted to the circuit board  80  using any suitable mounting technique, for example using a ball grid array  92  (see  FIGS. 4 and 5 ) that is compression bonded or soldered to the board. 
     The circuit board  80  also includes electric circuitry that electrically connects the driver circuitry of the optical core  90  and the electrical connector  82  so that electrical signals can be transmitted between the core  90  and the electrical connector  82 . The configuration and arrangement for providing electric circuitry on a circuit board for electrically connecting components is known in the art. 
     With reference to  FIG. 4 , the circuit board  80 , the optical core  90  and the electrical connector  82  are illustrated as being disposed generally on a first horizontal plane P 1 , while the optical fiber connector  60  and the biasing mechanism  70  are disposed generally on a second horizontal plane P 2  that is generally parallel to the first plane P 1  and spaced vertically beneath the first plane. In addition, the optical fiber connector  60  has a first optical axis OA 1  that is defined by the plane P 2  while the optical die element(s) on the optical core  90  has a second optical axis OA 2  that is generally perpendicular to the first optical axis OA 1 . 
     As a result of this arrangement, optical signals in the connector assembly  14  need to be deflected 90 degrees from the first optical axis OA 1  to the second optical axis OA 2  and vice versa. Further, the optical signals need to be transmitted between the optical fiber connector  60  and the optical core  90 . 
     As best seen in  FIGS. 4 and 5 , transmission of the optical signals between the optical fiber connector  60  and the optical core  90  is achieved using an optical fiber ribbon  100  while deflection of the optical signals is achieved using an optical deflecting device  102 . The fiber ribbon  100  is completely disposed within the housing structure  20  and has a first end  104  optically connected to the optical fiber connector  60  and defining the exposed ends  66  and a second end  106  optically connected to the optical deflecting device  102 . 
     The optical deflecting device  102  is also completely disposed within the housing structure and is mounted on the optical core  90  adjacent to the optical die element. The optical deflecting device  102  is configured to deflect an optical path to and from the optical die element of the optical core  90  and the second end  106  of the fiber ribbon  100 , whereby optical signals from the fiber ribbon  100  are appropriately deflected upward at the correct angle to be received by the optical die element(s) and whereby optical signals from the optical die element(s) are appropriately deflected at the correct angle into the second end  106  of the fiber ribbon. 
     The optical deflecting device  102  can be any device that can receive optical signals and deflect the path of the optical signals. A suitable optical deflecting device is the PRIZM® LightTurn® Ferrule, part number  14012  available from US Conec of Hickory, N.C. Another example of a suitable optical deflecting device that can be used is the lens array described in U.S. Pat. No. 7,399,125. 
     With reference to  FIG. 4 , the second end  106  of the fiber ribbon enters and connects to the optical deflecting device  102  at an angle α relative to a horizontal axis. In one embodiment, the angle α is less than or equal to approximately 8 degrees. In another embodiment, the angle α is equal to approximately 8 degrees. Because of the angle α, and because the optical signals enter/exit the optical fiber connector along the first optical axis OA 1  and enter/exit the optical die element(s) along the second optical axis OA 2 , the optical path of the signals are deflected a total angle of greater than or equal to approximately 90 degrees. For example, the optical path is deflected between approximately 90 degrees and 98 degrees. In another example, the optical path is deflected approximately 98 degrees. 
     Due to the fragile nature of the optical fiber ribbon  100  which is coupled to the moveable optical fiber connector  60 , the design of the connector assembly  14  accommodates the movements of the optical fiber connector  60  without damaging the optical fiber ribbon  100 . In particular, with reference to  FIGS. 4 and 5 , the optical fiber ribbon  100  is provided with a first curved region  110  between the ends  104 ,  106 . The first curved region  110  is disposed within the upper cavity  36  of the first package body  26 . If the optical fiber connector  60  moves backward, the first curved region  110  is pushed upward in the cavity  36  accommodating the movement of the connector  60 . The gap between the top of the curved region  110  and the cover  30  is sufficient to allow upward deflection of the curved region  110  through all anticipated movements of the connector  60 . 
     Additionally, as best seen in  FIG. 5 , the block  72  includes a slot  112  formed therein through which the fiber ribbon  100  passes while leading to the connector  60 . The width of the slot  112  is slightly greater than the width of the fiber ribbon  100  to permit minimal side-to-side shifting of the fiber ribbon  100  and to permit flexing of the fiber ribbon without frictionally engaging the sides of the slot  112 . The slot  112  further includes a sloped surface  114  that is positioned opposite or adjacent to a second curved region  116  in the fiber ribbon  100 . The second curved region  116  forms a smooth transition between the first curved region  110  and the horizontal extent of the fiber ribbon in the connector  60 . 
     Returning to  FIGS. 2-4 , once the other components are assembled, the cover  30  is applied to close off the open tops of the package body  26  and the package body  28  and protect the components inside the housing structure  20 . In one embodiment, the cover is adhesively bonded in place, but other attachment techniques can be used. 
     The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.