Abstract:
Optical routers or optical interconnection devices that include an optical coupling method and optical coupling apparatus wherein a plurality of layers that contain optical devices that require optical coupling can be optically coupled by inserting optical coupling elements therein to transfer a light signal from one location on one layer to another location on a different layer. The optical coupling elements can include various light directing members such as reflectors, beam splitters/combiners or other components that can act on a light signal to modify, or control the light signal in a desired manner. In addition, an optical coupling elements can be transparent to the light signal so as not affect the direction or the integrity of the light signal as it passes through the optical coupling element.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to optical routers or optical interconnection devices, and more specifically, to optical coupling elements that can direct optical signals within of a circuit board.  
       CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0002]     None  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0003]     None  
       REFERENCE TO A “MICROFICHE APPENDIX” 
       [0004]     None.  
       BACKGROUND OF THE INVENTION  
       [0005]     This invention relates to multi-layered devices that can be used for optical printed circuit boards (PCBs), optical backplanes, passive optical networks or other optical devices that require optical array interconnections. More particularly, this invention relates to optical interconnection devices that allow light signals to be transferred from one layer to another layer through one or more stackable optical coupling elements.  
         [0006]     Optical transmission paths are general formed of light conducting members that are arranged to intersect each other. These light conducting members, which can consist of optical fibers or optical waveguides, are generally supported on a substrate. Oftentimes the circuit boards and optical devices are stacked to form a multi-layer device. However, such multi-layer devices, although more compact then a set of unstacked single layer devices, fail to achieve the full benefit of stacking because it is difficult to directly route a light signal from one layer to another. In such stacked devices light is generally directed from one layer to another by having the light path on one layer extend to an external peripheral extension member where it is then sent to a second layer through another peripheral extension member on a second layer.  
         [0007]     In contrast to the prior art method, of using external peripheral extension members to transfer the optical signals from one layer to another, the present invention can directly transfer a light signal from one layer of a multi-layer device to one or more layers of the multi-layer device without the need for external peripheral extension members on each of the layers of the multi-layer device. Thus, the optical interface of the present invention can be used to connect active optical devices, passive optical devices and optical waveguides without the need for external peripheral extension members to transfer the optical signals from one layer to another.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention comprises an optical router that includes an optical coupling method and optical coupling apparatus wherein a plurality of layers that contain optical devices, which require optical coupling, can be optically coupled by inserting an optical coupling element or elements therein to transfer a light signal from one location on one layer to another location on a different layer. The optical coupling elements can include various light directing members such as reflectors, beam splitters or other components that can act on a light signal to modify, or control the light signal in a desired manner. In addition, an optical coupling element can be transparent to the light signal (i.e. passive) so as not affect the direction or the integrity of the light signal as it passes through the optical coupling element. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective, partially cut-away view of an optical interconnection device constructed in accordance with the invention that connects orthogonally aligned optical fiber layers;  
         [0010]      FIG. 2  is an view of three transparent optically coupling elements that are stacked in an end to end relationship;  
         [0011]      FIG. 3  is a perspective view of a transparent optical coupling element that contains at least two different light directing members embedded therein;  
         [0012]      FIG. 4   a  is a cross-sectional view of a point-to-point optical interconnection;  
         [0013]      FIG. 4   b  is a cross-sectional view of a point-to-many optical interconnection;  
         [0014]      FIG. 4   c  is a cross-sectional view of a blind optical via; and  
         [0015]      FIG. 4   d  is a cross-sectional view of a buried optical via; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The optical coupling elements of the present invention provide a compact, affordable and reliable optical interconnection device that extends network routing capability and enhances design flexibility. One can utilize the invention in optical backplanes, passive optical networks or other multi-layer devices having optical connections to allow one to efficiently and compactly interconnect the optical fibers in the different layers of a multi-layered device. Light directing members in the optical coupling elements include such light directing members as light splitters, light combiners and the like which can be fixedly embedded into a optical coupling element. The optical coupling elements can extend from layer to layer or can be stacked. In either case the optical coupling elements provide an optical coupler or optical interconnection device that can effectively transfer a light signal from one layer to another layer of a multi-layer device without having to direct the light signal to a remote peripheral extension.  
         [0017]     In general, one forms a multi-layer device from a plurality of layers or substrates that each contain optical fibers or optical waveguides that require some type of optical interconnection therebetween. Holes or passageways are then formed from one layer to another layer. In the present invention, one inserts optical coupling elements into the passageways or vias in the substrate layers to direct the light from one optical fiber in one layer to another optical fiber in another layer. The optical coupling elements allow one to receive light from an optical fiber in one layer and to transmit a light signal or a portion of the light signal to an optical receiver in an adjacent layer without having to divert the light signal to a peripheral extension member.  
         [0018]     To illustrate the invention reference should be made to  FIG. 1 .  FIG. 1  shows a perspective view of a two layer system  10  in a partial cut-away view. While the two-layer device  10  is shown for purpose of illustration, it is apparent the interconnection principles that are shown in  FIG. 1 , and described in conjunction therewith, are applicable to optical devices with three or more layers of optical fibers or other devices that require light signal connections between different levels of the optical devices.  
         [0019]     The two-layer optical system  10  comprises a first substrate  12  having a first set of parallel oriented optical fibers  14 ,  15 ,  16 ,  17  and  18  extending in a first direction, (which is designated as the “x” direction). For example, optical fiber  15  has one input/output face  15   a  at one end and a second input/output face  15   b  at the opposite end. A second substrate  12   a , which is layer proximate to substrate  12  also includes a set of parallel oriented optical fibers  19 ,  20 ,  21 ,  22 , and  23  that extend in a second direction, (which is normal to the first direction and is designated as the “y” direction). The optical fibers  14 - 23  can be conventional, commercially available optical fibers that are secured on the substrates  12  and  12   a , or they can be optical fibers that are embedded into the substrates  12  and  12   a  or they can be optical waveguides that are embedded unto substrates  12  and  12   a . The optical fibers, which are translucent bodies, can also be part of a polymer flexible circuit, in which case it is preferable that the fibers from a plurality of layers terminate in positions of a single multiple fiber optical connector, for example a conventional optical connector such as an MT style optical connector.  
         [0020]      FIG. 1 , illustrates how a light signal, which is identified by dashed line  27 , can be transmitted through optical fiber  17  in substrate  12  to the optical fiber  20  in the substrate  12   a , which is an adjacent layer, by the optical coupler or optical interconnection device  24  of the present invention. That is, the optical coupler device  24 , which comprises a lower optical coupling element  26  and an upper optical coupling element  28  which are in a stacked arrangement and positioned along the z axis. The optical coupling element  28 , which comprises a light transmitting medium, has a cylindrical shape. The entry/exit face  28   a  intersects the light signal  27  from optical fiber  17  in substrate  12 . The entry/exit faces are polished such that a light signal substantially passes through the entry/exit face rather than being reflected therefrom. The optical coupling element  28  includes an embedded light reflecting mirror  28   b  that directs the light signal  27  downward along the z axis to a second embedded light reflecting mirror  26   b  in optical coupling element  26 , also cylindrical in shape, that in turn directs the light signal  27  through an entry/exit face  26   a  and into optical fiber  20  where the light signal  27  travels therealong as indicated by the dashed line.  
         [0021]     The optical coupler device  24  can be inserted into passageways or vias that are formed at desired locations on a multi-layered board by laser drilling, or other types of channel forming operations. After the passageways or vias are formed one can press the individual optical coupling element into the vias in the substrates. In the embodiments shown, the length of the optical coupler  24  is sufficiently long so as to extend through substrate  12  and substrate  12   a . If it is desired to transmit a light signal from the plane of substrate  12  to a lower substrate layer or a higher substrate layer that are separated by intermediate layers the length of the light coupler  24  can be increased or deceased to accommodate the thickness of the layered substrates. In general the thickness of each optical coupling element math the thickness of to corresponding substrate layer it is passing light through.  
         [0022]      FIG. 2  shows an exploded view of an optical coupler or optical interconnection device  30  comprising a plurality of three stackable, optical elements  31 ,  32  and  33 . Optical elements  31 ,  32  and  33  each comprise optical routing elements that route a light signal from one surface of the optical element to another surface of the optical elements. Each of the optical coupling element has a flat top end surface and a flat bottom end surface to permit stacking in an end-to-end relationship. A dashed line  35  indicates the path a light signal follows as it passes through optical elements  31 ,  32  and  33 .  
         [0023]     Optical coupling element  31  has a cylindrical optical entry face  31   a  and a planer optical exit or end face  31   c  with the optical exit face  31   c  also comprising an optical stacking face. By optical stacking face it is understood that another light signal routing element can be stacked proximate the optical stacking face  31   c  without substantially hindering or degrading the passage of the light signal therethrough. Embedded and fixedly suspended within the optical coupling element  31  is a light directing member, which comprises a mirror  3 l b  that deflects a radially entering light signal  35  from the optical coupling element entry face  31   a  to the optical coupling element exit face  31   c.    
         [0024]     Positioned proximate optical coupling element  31  is a passive optical coupling element  32  that has a top exit/entry face  32   d  and a lower exit/entry face  32   c . Exit/entry face  32   d  is stackable with face  31   c  so as to permit light signal transfer without substantial degradation. Similarly, the exit/entry face  32   c  is stackable with exit entry face  33   d  of coupling element  33  to permit light signal  35  transfer thereto without substantial degradation thereof. The coupling element  32  is described as a passive element as the light signal  35  is not interrupted by a member embedded in element  32 .  
         [0025]     Located below optical element  32  is a third optical element  33  having a top exit/entry face  33   d  and a cylindrical exit/entry face  33   a . A mirror  33   b  is embedded in optical coupling element  33  to deflect the light signal from an axial direction to a radial direction.  
         [0026]     The optical coupler  30  comprises a set of cylindrical shaped optical coupling elements that allows each of element  31 ,  32 , and  33  to be rotated to different angular positions so the light can be directed in the proper direction. As shown in  FIG. 2 , the output light beam off of the embedded mirror or reflecting plate  33   b  is directed in the same direction as the input beam impinging on embedded mirror or reflecting plate  31   b . Thus, with this configuration light from one set of optical fibers oriented in the x direction can be sent to another optical fiber in a different layer that is also oriented in the x direction. However, if one wants to direct the light signal in a different direction one can rotate optical element  33  to direct the light signal  35  in a different direction.  
         [0027]     Another optical coupling element  36  is shown in  FIG. 3 . Optical coupling element  36  comprises a single cylindrical optical coupling element having a cylindrical exit/entry face  36   a  and a set of three embedded light directing members suspended at different levels in the optical element  36 . Optical coupling element  36  includes a first light deflecting mirror  36   b , a second beam splitting plate  36   c  and a second light deflecting mirror  36   c . In operation of the optical coupling element  36  a light signal represented by dashed line  37  enters through exit/entry face  36   a  and is deflected axially downward until the light signal  37  impinges on light beam splitter  36   c . The light beam  37  then splits into a first light signal  37   a  which is directed radially outward of optical coupling element  36  and a second light signal  37   b  that passes axially downward into mirror  36   c  and is eventually deflected radially outward though exit/entry face  36   a . Thus an optical coupling element of the present invention can contain two or more embedded optical deflecting members therein.  
         [0028]     The embodiment of  FIGS. 4   a ,  4   b ,  4   c  and  4   d  illustrate different optical interconnection devices using various combinations of three different optical coupling elements. Each optical element is the same thickness as the interconnect layer so that the number of elements in each passageway is equivalent to the number of layers. The optical interconnection devices illustrated in  FIGS. 4   a ,  4   b ,  4   c  and  4   d  are comprised of optical coupling elements with three different types of embedded light directing members. The first type is an embedded mirror or light reflecting device that deflects the signal at a 90 degree angle. This optical element is referred to as a “90 degree turn” element The second type is an optical coupling element without an embedded member that allows the light to pass through without being affected. This optical element is referred to as a “pass through element” . The third type is an optical coupling element containing an embedded beam splitter and combiner and is referred to as a “splitter/combiner” optical element. This type of element can separate a light signal into two light signals or alternately combines two light signals into one light signal.  
         [0029]      FIG. 4   a  shows a “point-to-point” optical interconnection system  40 . The system  40  includes a first layer  41 , a second layer  42  and a third layer  43  which are stacked on one another. A first optical receiving device  44  is located in one position on top of layer  41  and a second optical transmitting device  45  is also located on top of layer  41 . A light signal, which is represented by solid line  46 , is shown extending from device  45  to device  46  thorough a set of optical coupling elements located in layers  41 ,  42  and  43 . In the “point-to-point” arrangement the optical interconnections devices comprises passive “pass through” optical coupling elements  47  and  48  that allow light signal  46  to pass through without affecting the light signal. After the light signal  46  passes though optical coupling element  48  it enters a “90 degree turn” element  49  that directs the light signal  46  to a second lateral positioned “90 degree turn” element  50 . The light signal  46  is then directed through “pass through” optical coupling elements  51  and  52  which direct the light signal into device  44 .  
         [0030]      FIG. 4   b  shows a “point-to-many” optical intersection system  60  containing three optical interconnection devices. This system contains a first layer  61 , a second layer  62  and a third layer  63  with a first optical device  64 , a second optical device  65  and a third optical device  66  all positioned on top of layer  61 . In the system illustrated in  FIG. 4   b , a light signal  67  from optical device  64  is split into a first light signal  67   a  that is directed into optical device  65  and a second light signal  67   b  that is directed into optical device  66 . The first optical interconnection device comprises two “pass through” elements  68  and  69  and a “90 degree turn” element  70  that directs the light signal into a “splitter/combiner”  71  which in turn directs light signal  67   a  axially upward through “pass through” elements  73  and  72  and into optical device  65 . A portion of light beam  67 , which emerges as light beam  67   b , is directed into “90 degree turn” element  74  which directs the light signal  67   b  through “pass through” elements  75  and  76  and into optical device  66 .  
         [0031]      FIG. 4   c  shows a “blind optical via” system  80 . System  80  includes a first layer  81 , a second layer  82  and a third layer  83  with an optical device  84  and an optical device  85  located on top of layer  81 . A light signal  86  is shown traveling from optical device  84  to optical device  85  without entering the third layer  83 . In this arrangement, the optical coupling element  87  comprises a “pass through” element and the second optical element  88  comprises a “90 degree turn” element which directs the light signal  86  into a second “90 degree turn” element  90  and therefrom to a “pass through” element  89  that directs the light signal  86  into the optical device  85 . In the “blind optical via” system one can pass an optical signal through less than all of the layers of stacked circuit boards.  
         [0032]      FIG. 4   d  shows a “buried optical via” system  100 . System  100  includes a first layer  101 , a second layer  102 , a third layer  103  and a fourth layer  104 . Located on top of layer  101  is a first optical device  106  and a second optical device  105 . In this system, a light signal  107  is transmitted from device  106  to device  105 . A first “pass through” element  108  directs a light signal to a “90 degree turn” element  104  in layer  102 . The light signal  107  is then directed to a “90 degree turn” element  104  in layer  102  and then axially downward to a second “90 degree turn” element  110  in layer  103 . As can be viewed in the illustrations, each of the “90 degree turn” elements  109  and  110  have a layer adjacent thereto where there is no optical coupling element. The light single  107  is emitted from element  110  and enters “90 degree turn” element  111  and is directed axially upward through “pass through” elements  112  and  113  into the optical device  105 .  
         [0033]     The above arrangements of optical coupling elements are intended to illustrate how one can stack the various optical coupling elements to provide for different optical paths through stacked layers.  
         [0034]     An optical routing or interconnection device in accordance with the invention may consist of multiple stacked coupling elements, as shown in  FIG. 2  or single multi-function coupling elements as shown in  FIG. 3 . The illustrated configurations and the elements described herein are examples of the variety of optical light beam controlling applications that can be implemented within the scope of the present invention through combinations of various optical elements. Although each of the coupling elements are shown as having a cylindrical shape other uniform or non-uniform geometric shapes with multiple sides could also be used.  
         [0035]     While the present invention is particularly useful with multi-layer substrates the invention is also useable with a single substrate when a light signal needs to be transferred from a first location within the substrate to a second location within the substrate.