Abstract:
An optical coupling system includes a first unit including a source of light or a first multi-core optical fiber, each of the source and the first multi-core optical fiber including at least a first aperture, a second unit including a second multi-core optical fiber including at least a second aperture corresponding to the first aperture of the first unit, and a lens array unit redirecting light between the first unit and the second unit, the lens array unit substantially matching light rays transmitted or received between the first aperture of the first unit and the corresponding second aperture of the second unit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The disclosed invention relates generally to integrated circuits and silicon chip technology, and more particularly, but not by way of limitation, the packaging of optoelectronic devices in a dense and integrated manner. 
         [0003]    2. Description of the Related Art 
         [0004]    Optical transceivers are increasingly used to enable data communication between and within computers. An optical transceiver can transmit and receive data using optical fiber rather than electrical wire. The optical fiber can be used to facilitate the transfer of information in light beams, rays or pulses along solid transparent fibers or cables. One of the major advantages of optical technology is its high transfer rate. 
         [0005]    However, today&#39;s optical transceiver packages are bulky, complex and expensive. The performance of high-end computers systems continues to improve as the number of processing cores (and their speed) is increased. This increase in the number of processors requires a corresponding improvement in the system&#39;s interconnect bandwidth. Today&#39;s high-end supercomputer systems are being built with hundreds of thousands of individual optical fibers to transmit this data, at considerable expense. 
         [0006]    The communication bandwidth between computers and within a computer is playing an increasing role in a system&#39;s overall performance. The trend towards multi-core processors and multiple processors per machine requires an increase in communication between processors and between a processor and its memory. Electrical data links perform well over short distances, but they reach a limit as the link distance and frequency increases. Optical data links over fiber are capable of high speed communication with low loss over large distances. However, current optical transceivers are bulky and expensive compared with their electrical counterparts. 
         [0007]    Currently, a standard 12 channel optical transceiver can be mated with a 12 fiber ribbon cable, with each fiber containing only 1 core. However, a single core in the optical fiber increases the space that is used by the arrangement and can be expensive. 
         [0008]    Recently it has been proposed to use multiple graded index and/or single mode cores inside a single optical fiber to save space and reduce cost. What is needed is a means to couple the light into and out of these new multi-core fibers in a simple and low cost manner. In further detail, what is also needed is a means to couple light from OE (opto-electronic) devices, such as VCSELs (vertical cavity surface emitting lasers) and photodiodes, into a multi-core fiber. 
         [0009]    There is a related art method to couple multi-core fiber to a VCSEL/PD (vertical cavity surface emitting lasers/photodiode) array. In this case the multi-core fiber contains 4 cores. The multi-core fiber is butt coupled to a 4 element VCSEL array. 
         [0010]    However, the multi-core fiber must be close to the active device of the VCSEL array for best coupling, but not touch the VCSEL array. If the fiber touches the VCSEL array, then the VCSEL array may be damaged. There is possible damage during assembly, and the optical fiber is not easily connectorized. 
         [0011]    Another problem relates to the NA (numerical aperture) of the VCSEL that may be greater than a typical NA of a multi-mode fiber. Therefore, given this mismatch in NAs, a coupling loss may occur, leading to a lower overall optical coupling efficiency. Therefore, the VCSEL NA not matching, but instead overfilling the fiber NA, leads to lower efficiency. These limitations reveal that the fiber-to-VCSEL “butt” coupling method is less than optimal. 
         [0012]    In another arrangement, a long focal length dual lens optical coupling arrangement shows poor optical performance when used with a multi-core fiber. The long focal length dual lens optical coupling arrangement has been previously used to couple light between single core optical fibers rather than a multi-core fiber. A relatively long focal length lens can successfully image the core from one fiber to another. 
         [0013]    However, when a multi-core fiber is used, the cores are offset from the center axis of the lens. The object (core) offset causes light from the source to miss a portion of the collimating lens, leading to a loss of light (lower efficiency) and potential cross-talk between neighboring fibers. 
         [0014]    Another arrangement includes a short focal length dual lens optical. In this case the focal length of the collimating lenses or telecentric lens pair is short so that the light from the offset source does not miss the collimating lens. However, given the lens short focal length and the offset source, it is difficult to focus the light into the multi-core fiber. For example, the light ray misses the core of the multi-core fiber. The offset sources requires tight lens manufacturing tolerances. The alignment tolerances of optoelectronic elements (OE), such as VCSEL, in the X, Y, and Z axis are critical. The light rays at the multi-core fiber are abberated and overfill the cores, possibly leading to a drop in coupling efficiency and a potential for cross-talk between optical channels. 
         [0015]    Accordingly, it is desirable to provide an apparatus and method to optically interconnect a multi-core optical fiber with a compact optical transceiver in order to improve optical coupling performance, and to have a simpler package and lower cost. Moreover, concerning the desire for improved optical coupling performance, there is a desire to reduce or avoid a loss of light and potential for cross-talk between optical channels. 
         [0016]    In addition, it is also desirable to provide a means to reduce the number of optical transceivers needed by a computer system by using multi-core optical fibers to increase the number of optical channels while maintaining or reducing the optical transceiver&#39;s package size. 
       SUMMARY OF INVENTION 
       [0017]    In view of the foregoing and other problems, disadvantages, and drawbacks of the aforementioned background art, an exemplary aspect of the disclosed invention provides a means to optically interconnect multi-core optical fiber with a compact optical transceiver by using unique optical elements, thereby leading to improved optical coupling performance, a simpler package and lower cost. 
         [0018]    Moreover, an exemplary aspect of the disclosed invention also provides a means to reduce the number of optical transceivers needed by a computer system by using multi-core optical fibers to increase the number of optical channels while maintaining or reducing the optical transceiver&#39;s package size. 
         [0019]    In addition, a disclosed exemplary embodiment of invention provides a means to interconnect a transceiver with an optical fiber containing multiple cores instead of the standard single core optical fibers, thereby dramatically increasing the number of available optical channels without increasing the transceiver&#39;s package size and costs. 
         [0020]    In accordance with one exemplary aspect of the disclosed invention, an optical coupling system includes a first unit including a source of light or a first multi-core optical fiber, each of the source and the first multi-core optical fiber including at least a first aperture, a second unit including a second multi-core optical fiber including at least a second aperture corresponding to the first aperture of the first unit, and a lens array unit redirecting light between the first unit and the second unit, the lens array unit substantially matching light rays transmitted or received between the first aperture of the first unit and the corresponding second aperture of the second unit. 
         [0021]    Moreover, the array unit can include a field lens configured to redirect light toward a center of a light path from the first unit to the second unit. The lens array unit can also include a dual sided lens array including a field lens facing the first unit and a collimating lens on another side of the field lens to redirect light toward a center of a light path from the first unit to the second unit. The lens array unit can also include a dual sided lens array, where the dual sided lens array includes a first dual sided lens including a field lens facing the first unit and a collimating lens on another side of the field lens to redirect light toward a center of a light path from the first unit to the second unit, and a second dual sided lens including a field lens facing the second unit and a collimating lens on another side of the field lens to receive or send light between the first and second dual sided lenses in order to redirect light toward a center of a light path from the first unit to the second unit. 
         [0022]    The optical coupling system can also include a field lens arranged on the first unit. The first unit can include the first multi-core optical fiber. The lens array unit can include a lens pair, with a first lens having a focal length different than a focal length of a second lens to select a magnification or reduction of transmitted and received light in order to reduce a numerical aperture of light received at the second multi-core optical fiber or the first multi-core optical fiber. 
         [0023]    The lens array unit can include a first dual sided lens being adjacent to the first unit, and a second dual sided lens being adjacent to the second unit and having a focal length greater than a focal length of the first dual sided lens. The first unit can include the source including at least two source points set apart, and the lens array unit includes a curved mirror field lens and a reflective prism element that translates the light beams towards an optical centerline between the first unit and the second unit. 
         [0024]    The first unit can include the first multi-core optical fiber, and the first and second multi-core optical fibers each have a convex shaped end facing the lens array unit to redirect light toward a center line of an optical path between the first unit and the second unit. The source in the first unit can include a vertical cavity surface emitting laser (VCSEL) and/or a photodiode (PD) array. 
         [0025]    The optical coupling system can also include the source in the first unit including an opto-electronic (OE) module including the lens array unit with conductive wiring. The source in the first unit can include an opto-electronic (OE) module including the lens array unit with conductive wiring. 
         [0026]    The optical coupling system can also include the source in the first unit including a complementary metal-oxide semiconductor device integrated with laser diode drivers/trans-impedance amplifier (CMOS LDD/TIA) with an opening for an insertion of the lens array unit. The source in the first unit can include an OE module, and the lens array unit can include a dual sided lens array attached to a ferrule optical connector. 
         [0027]    The source in the first unit can include an OE module, and the lens array unit can include a dual sided lens array with an optical connector including dual lenses, a turning mirror, and guide holes for the second multi-core optical fiber. The second unit can include a flat portion in a fiber cladding and a corresponding flat portion in a fiber ferrule for fiber rotational orientation. 
         [0028]    The second unit can include a groove in a fiber cladding of the second multi-core optical fiber for fiber rotational orientation. The optical coupling system can also include a dual sided lensed optical connector to couple the second multi-core optical fiber of the second unit with the lens array unit and the first unit. 
         [0029]    In accordance with still another exemplary aspect of the disclosed invention, a telecentric imaging system for an optical coupling device includes an array of dual sided lenses, including a first dual sided lens unit including a lens facing a source object of light to direct light from the source to a multi-core optical fiber toward an optical center line between the source and the multi-core optical fiber, and a second dual sided lens unit set apart from the first dual sided lens unit, the second dual sided lens unit being next to the multi-core optical fiber to direct light between the source and the multi-core optical fiber unit toward the optical center line between the source and the multi-core optical fiber unit. 
         [0030]    The first dual sided lens unit includes a first field lens facing the source object and a first collimating lens on another side of the first dual sided lens unit to direct light toward an optical center line between the source and the multi-core optical fiber, and the second dual sided lens unit includes a field lens facing the multi-core optical fiber unit and a second collimating lens facing the first collimating lens to direct light toward an optical center line between the source and the multi-core optical fiber unit. 
         [0031]    At least one of the first dual sided lens unit and the second dual sided lens unit includes a field lens to direct light from an aperture of the source object to a corresponding aperture of the multi-core optical fiber. At least one of the first dual sided lens unit and the second dual sided lens unit includes field lens means to substantially match the light received to apertures of the multi-core optical fiber. 
         [0032]    In accordance with yet another exemplary aspect of the disclosed invention, a method of an optical coupling system includes transmitting light from a source object to a multi-core optical fiber, receiving the light, by the multi-core optical fiber, from the source object, and redirecting light, by a dual-sided lens array, from the source object to the multi-core optical fiber, the dual-sided lens array substantially matching light rays emitted from points of the source object and light rays received at corresponding points of the multi-core optical fiber. The redirecting of light can include redirecting the light toward a center of a light path from the source object to the multi-core optical fiber by the dual-sided lens array including a field lens. 
         [0033]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0034]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0035]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0036]    The exemplary aspects of the invention will be better understood from the following detailed description of the exemplary embodiments of the invention with reference to the drawings. 
           [0037]      FIGS. 1A and 1B  illustrate side and end views, respectively, of a multi-core fiber butt coupled to a VCSEL array of the related art. 
           [0038]      FIG. 2  illustrates a side view of a long focal length dual lens optical coupling arrangement the related art. 
           [0039]      FIG. 3  shows a side view of a short focal length dual lens optical coupling arrangement of a related art. 
           [0040]      FIGS. 4A to 4C  illustrate side views of a dual lens with field lens approach optical coupling arrangement of exemplary embodiments of the invention. 
           [0041]      FIG. 5  shows a side view of the dual lens with field lens approach optical coupling arrangement of an exemplary embodiment of the invention where the object (VCSEL) is magnified on the image (fiber) side. 
           [0042]      FIG. 6  shows another exemplary embodiment of the invention where the object source points are moved apart and a dual mirror translates the light beams towards the optical centerline. 
           [0043]      FIG. 7  shows an opto-electronic package incorporating a lens plate with wiring, attached CMOS drivers/TIA circuits, attached OE devices, mounted on a substrate interconnecting with a ferrule containing multi-core fiber and attached dual sided lens plate in an exemplary embodiment. 
           [0044]      FIG. 8  shows an opto-electronic package incorporating a CMOS device with integrated drivers/TIA circuits with an opening to accommodate a dual sided lens array in an exemplary embodiment. 
           [0045]      FIG. 9  shows an opto-electronic package with integrated lens plate which mates with an optical connector containing dual lens arrays and a turning mirror to bend the light at an angle in an exemplary embodiment. 
           [0046]      FIGS. 10A and 10B  show an exemplary embodiment of a multi-core fiber dual lens connector mating with a similar connector. 
           [0047]      FIG. 11A  shows an end view of a conventional fiber in ferrule connector 
           [0048]      FIG. 11B  shows an end view of a fiber (with flat for alignment) in a keyed ferrule in exemplary embodiment of the invention. 
           [0049]      FIG. 11C  illustrates notches on fiber to facilitate multi-core fiber rotation alignment in an exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0050]    The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. It is emphasized that, according to common practice, the various features of the drawing are not necessary to scale. On the contrary, the dimensions of the various features can be arbitrarily expanded or reduced for clarity. 
         [0051]    The current standard, for example, is a 12 channel optical transceiver mating with a 12 fiber ribbon cable, with each fiber containing only a single core. However, an exemplary aspect of the invention provides a means to interconnect a modified version of today&#39;s transceiver with an optical fiber containing multiple cores, thereby dramatically increasing the number of available optical channels without increasing the transceiver&#39;s package size. 
         [0052]    Therefore, an exemplary embodiment in accordance with the invention provides an apparatus and technique to optically interconnect multi-core optical fiber with a compact optical transceiver by using unique optical elements, thereby leading to improved optical coupling performance, a simpler package and lower cost 
         [0053]    Typical single core multi-mode fibers have a cladding diameter of 125 microns and a core size of 50 microns. Newer multi-core multi-mode fibers may contain 2 or more cores surrounded by cladding with a diameter of 80 microns or more, typically 125 microns. By including more cores in a 125 micron clad fiber, more optical channels are available for data transmission, thus increasing the fiber&#39;s optical bandwidth. As mentioned previously, there is a need for an apparatus and technique to couple light from OE (opto-electronic) devices, such as VCSELs and photodiodes, into a multi-core fiber. 
         [0054]    Referring to  FIGS. 1A and 1B , a method to couple multi-core fiber to a VCSEL/PD (vertical cavity surface emitting lasers/photodiode) array is provided of the related art. In this case the multi-core fiber  12  contains 4 cores each with a core size of 50 microns, in a cladding of 125 microns. The fiber is butt coupled to a 4 element VCSEL array  10 . However, there are a plurality of problems in such proposals of butt coupling the VCSEL/PD array  10  with the multi-core fiber  12 . 
         [0055]    For example, the multi-core fiber  12  must be close to the active device of the VCSEL array  10  for best coupling, but not touch the VCSEL array  10 . If the fiber touches the VCSEL array  10 , then the VCSEL array  10  may be damaged. Therefore, there is possible damage during assembly and such an arrangement is not easily connectorized. 
         [0056]    The NA (numerical aperture) of the VCSEL is typically 0.25-0.3, which may be greater than a typical multi-mode fiber which has an NA of 0.2-0.25. Therefore, given this mismatch in NAs, a coupling loss may occur, leading to a lower overall optical coupling efficiency. Therefore, the VCSEL NA (numerical aperture) not matching, but instead overfilling the fiber NA, leads to lower efficiency. These limitations reveal that the optical fiber to VCSEL ‘butt’ coupling method is less than optimal. 
         [0057]    Referring to  FIG. 2 , a long focal length dual lens optical coupling arrangement  20  of a related art shows poor optical performance when used with a multi-core fiber  26 . The long focal length dual lens optical coupling arrangement has been previously used to couple light between single core optical fibers rather than a multi-core fiber. With a single core of 50 microns diameter the object (core) radius is 25 microns. A relatively long focal length lens, between 400-1000 microns focal length, can successfully image the core from one fiber to another. 
         [0058]    However, when a multi-core fiber  26  is used, the cores are offset from the center axis of the lens, typically by 30 or more microns. The source  20  transmits through the collimating lens or telecentric lens pair  22  and  24  to the multi-core fiber  26 . The object (core) offset causes light  28  (e.g., light ray  28   a ) from the source  21  to miss a portion of the collimating lens  22 , leading to a loss of light (lower efficiency) and potential cross-talk between neighboring fibers. The offset source also overfills the lens aperture (for, e.g., a 250 μm lens pitch). Therefore, there is optical power lost and also potential for crosstalk. 
         [0059]    Referring to  FIG. 3 , a short focal length dual lens optical coupling arrangement  30  of a related art is provided. In this case the focal length of the collimating lenses or telecentric lens pair  32  and  34  is short, typically between 100-400 microns, so that the light from the offset source  21  does not miss the collimating lens  32  or  34  as occurring with the longer focal length collimating lenses  22  and  24  of  FIG. 2 . However, given the short focal length of the lens and the offset source  21 , it is difficult to focus the light  38  into the multi-core fiber  26 . For example, light ray  38   a  misses the core of the multi-core fiber  26 . The offset sources require tight lens manufacturing tolerances. The alignment tolerances in the X, Y, and Z axis of opto-electronic elements (OE), such as VCSEL, are critical. The light rays at the multi-core fiber are abberated and overfill the cores, leading to a drop in coupling efficiency and a potential for cross-talk between optical channels. 
         [0060]    Referring to  FIG. 4A , a dual lens with a field lens provides an optical coupling arrangement  40  of an exemplary embodiment of the invention. In this arrangement of the optical coupling device  40 , a field lens  48   a  is added next to the source  50  and a field lens  48   b  is added next to the multi-core fiber  46 . The source or sources  50  can be, for example but not limited to, a VCSEL source. 
         [0061]    The field lens  48  is configured to redirect the light  52  from the source  50  towards the center of the collimating lens  42 , thereby passing all the light  52  through the imaging system of the arrangement for the optical coupling device  40  and thus eliminating the optical inefficiencies described in, for example,  FIG. 2 . 
         [0062]    Moreover, given the longer focal length of the collimating lens, it is possible to realize a high image quality at the input to the multi-core fiber  46 , thus eliminating the potential for cross-talk between cores. 
         [0063]    In further detail, referring again to  FIG. 4A , with the addition of the field lens  48   a  and  48   b , the field lens points the off-axis source rays toward the lens center  54 . Therefore, with such a configuration, there is a reduction in the aberration of off-center rays. In addition, the optical loss due to aberration is minimized. Moreover, telecentricity is maintained in the dual lens with field lens approach optical coupling apparatus  40 . Therefore, a telecentric imaging system can be provided with the addition of the field lens. Additionally, normal (longer) focal length lenses are also possible, which simplifies lens manufacture. 
         [0064]    Referring to  FIG. 4B , another exemplary embodiment is provided of an optical coupling system  60 . A telecentric imaging system is provided with a field lens  64  added on top of the OE device (e.g., VCSEL, PD, etc.)  62  in the optical coupling system  60 . A collimating lens pair  66   a  and  66   b  directs the light rays from the field lens  64 . A field lens  70  can be provided next to the multi-core fiber  72 . With the addition of the field lens  64  on the OE device  62 , the field lens  64  receives the light rays  68  from the source of the OE device  62  and points the off-axis source rays toward the lens center. 
         [0065]    Therefore, the field lenses  64  and  70  are configured to redirect the light  68  from the source of the OE device  62  towards the center of the collimating lens  66   a  and  66   b  thereby passing all the light  68  through the imaging system of the optical coupling system  60  and thus eliminating the optical inefficiencies of the related art addresses the concept of adding a field lens on the OE (VCSEL, PD) device. 
         [0066]    The field lens  64  can be added on top of the OE device (e.g., VCSEL, PD, etc.)  62  by, for example, depositing a transparent photoresist on the OE, patterning and developing a mesa array, then reflowing the photoresist in an oven to form a convex lens. 
         [0067]    Referring to  FIG. 4C , another exemplary embodiment is provided of an optical coupling system  80 . The optical coupling system is a multi-core fiber to multi-core fiber coupler. The multi-core fiber end portions  82  and  92  are curved to provide the function of a field lens. 
         [0068]    In further detail, the multi-core fiber  94  has an end portion  82  that transmits the light toward a plane surface  84  of the collimating lens  86   a  and/or receives the light from the plane surface  84 . The end portion  82  of the multi-core fiber  94  is shaped with a curved surface (e.g., convex shape) to provide a function of a field lens. 
         [0069]    A second plane surface  90  is provided at an end of the collimating lens  86   b  next to the second multi-core fiber  96 . The end portion  92  of the multi-core fiber  96  is also shaped with a curved surface (e.g., convex shape) to provide a function of a field lens. 
         [0070]    Therefore, a telecentric imaging system is provided with a convex shaped curved surface for the end portion  82  of the first multi-core fiber  94  and for the end portion  92  of the second multi-core fiber  96  in the optical coupling device  80 . The collimating lens pair  86   a  and  86   b  directs the light rays between the end portions  82  and  92 . The end portions  82  and  92  function as field lenses in order for the off-axis rays  88  toward the center of the collimating lens  86 . 
         [0071]    Therefore, the end portions  82  and  92  of the first and second multi-core fibers  94  and  96 , respectively, are configured to redirect the light  88  toward the center of the collimating lens  86 , thereby passing all the light  88  through the imaging system of the optical coupling device  80  and thus eliminating or reducing optical inefficiencies. 
         [0072]    Forming a convex surface (to be used as the field lens) on the end portions  82  and  92  of the first and second multi-core fibers  94  and  96 , respectively, can be accomplished by using a CO 2  laser to cleave and melt the multi-core fibers  94  and  96  to form a convex surface on the end portions  82  and  92  of the multi-core fibers  94  and  96 , respectively. 
         [0073]    Referring to  FIG. 5 , a dual lens with field lens approach for an optical coupling arrangement  200  is provided. The object (e.g., VCSEL)  210  is magnified on the image (fiber) side (multi-core fiber  214 ) as shown. In this case the arrangement is similar to that of  FIG. 4 . However, the focal length of the collimating lenses  212   a  and  212   b  are different from each other in order to realize a magnification or reduction of the source to the image (multi-core fiber  214 ). 
         [0074]    The source collimating lens  212   a  focal length is  600  microns and the image focusing lens  212   b  is 900 microns. Therefore, the source is magnified by 1.5×. As seen on the object  210 , a distance A is provided between the sources, and when the light rays transmit through the lenses  212 , the distance between the cores of the multi-core fibers is increased to a distance B. This magnification reduces the NA by that same factor. Hence the VCSEL (object  210 ) NA of 0.25 is reduced to an NA of 0.17 on the image side, making the NA more compatible with the NA of multi-core fibers  214  and improving the coupling efficiency as compared, for example, with the butt coupling approach shown in  FIG. 1 . 
         [0075]      FIG. 6  shows another exemplary embodiment, where the object source points  242  are moved apart and a dual mirror (curved mirror field lens  244  and reflective prism element  246 ) translates the light beams towards the optical centerline  250 . In this arrangement, the light beam reflecting elements (curved mirror field lens  244  and reflective prism element  246 ), which replace the field lens, are built into the source lens element. These reflecting elements allow the VCSEL array at the source to be fabricated with the source elements widely separated. This may be advantageous for some VCSEL designs where more room is needed for the VCSEL source metallurgy and interconnect contacts. 
         [0076]    Referring to  FIG. 7 , an opto-electronic package  300  incorporates a lens plate with wiring  366 , attached CMOS drivers/TIA circuits (e.g., CMOS LDD/TIA  382 ), attached OE devices (e.g., VCSEL/PD  384 ), mounted on a substrate  362  interconnecting with a ferrule  370  containing multi-core fibers  390  and attached dual sided lens plate  372 . With this arrangement of the opto-electronic package  300 , the source lens plate  366  incorporates the field lens and collimating lens. These lenses can be a single pair or an array of pairs as provided, for example, by the lens array  368 . Typically, for example, arrays consist of a row of 12 lens pairs or multiple rows of 12 lens pairs. Wiring is patterned on the lens plate  366  along with pads (e.g., C4s as interconnects  364 ) in order to mount a VCSEL or PD array  384  and to mount a CMOS (Complementary Metal-Oxide Semiconductor) laser driver array (LDD) or a photodiode transimpedance amplifier array (TIA) device (i.e., CMOS LDD/TIA)  382 . The lens plate  366  may then be mounted on a substrate containing the next level of interconnects such as a ball grid array or a land grid array (BGA/LGA)  362 . Above the lens plate  366 , a ferrule  370  containing multi-core fibers  390  and a dual-sided lens plate  372  is positioned to couple the light from and/or to the OE module to the fiber ribbon. 
         [0077]    Referring to  FIG. 8 , an opto-electronic package  400  similar to the opto-electronic package  300  of  FIG. 7  is provided. However, the lens plate  366  is replaced with a complementary metal-oxide semiconductor device with integrated laser diode drivers or trans-impedance amplifier circuits (CMOS LDD/TIA chip)  406  and an opening  408  in the CMOS device (CMOS LDD/TIA chip  406 ) is fabricated to accommodate a dual sided lens array (dual-sided lens plate)  474  of the dual-sided lens pair of  472  and  474 . Therefore, the CMOS LDD/TIA chip  406  is provided with an opening  408  for the dual-sided lens array  474  to be inserted. 
         [0078]    Wiring is patterned along with pads (e.g., C4s as interconnects  364 ) in order to mount a VCSEL or PD array  384  in a substrate  480  and to mount the CMOS LDD/TIA  406 . The substrate  480  can contain the next level of interconnects such as a ball grid array or a land grid array (BGA/LGA)  362 . 
         [0079]    Referring to  FIG. 9 , an opto-electronic package  500  with an integrated lens plate similar to that of  FIG. 7  is provided (i.e., integrated lens plate  366  having dual-sided lens  368 ). However, the fiber ferrule (i.e., ferrule with the multi-core fiber  370 ) with the dual-sided lens plate  372  (See  FIG. 7 ) is replaced with an optical connector (i.e., low profile lensed fiber connector  552 ) for the multi-core optical fiber  554  containing dual-sided lens arrays  550  and a turning mirror  548  to bend the light at an angle (See  FIG. 9 ). 
         [0080]    Referring to  FIG. 10A , an example of a multi-core fiber dual lens connector  600  is provided as another exemplary embodiment. In this case, a dual sided lens array  606 , serving as the field lens and the collimating lens, may be attached to the end of the ferrule  604  with the multi-core fiber  602 . 
         [0081]    Referring to  FIG. 10B , two multi-core fiber ferrules  600  are mated together at connection point  704  to form mated lensed multi-core fiber connectors  400  in another exemplary embodiment. By using the two dual sides lens arrays  606 , the optical imaging performance is maintained despite the offset sources of the multi-core fiber  602 . 
         [0082]    Referring to  FIG. 11A , an end view of a fiber in ferrule connector  1000  of a related art is provided. The optical fibers  1002 , for example, are arranged 12 per row, with a single ferrule  1004  containing a single or multiple rows in a single housing. In this case since single mode fibers (fiber with a single core  1002 ) are used, the fiber&#39;s rotational orientation with the ferrule guide hole is not a concern. 
         [0083]    Referring to  FIG. 11B , an end view of a multi-core fiber  1104  with an alignment flat  1102  fabricated as part of the optical fiber cladding to form the fiber in ferrule connector  1100  is provided as an exemplary embodiment of the invention. The flat  1102  on fiber is to facilitate multi-core fiber  1104  rotational alignment. The cores of the multi-core fiber  1104  are accurately positioned in the cladding with respect to the flat  1102  or other alignment feature. This flat alignment  1102  may then be used to rotationally orientate the optical fiber  1104  within the ferrule  1106 . The ferrule  1106  is fabricated to contain a hole with a flat  1102  or other feature that will accept the fiber  1104  and define its rotational orientation. 
         [0084]    Referring to  FIG. 11C , another fiber rotational alignment structure  1200  of an exemplary embodiment of the invention is shown. In addition to a flat  1102  on the fiber  1104  shown in  FIG. 11B , the multi-core fiber  1222  could have a v-groove  1226 , a rounded groove  1228 , a rectangular-shaped groove  1230  or other feature or equivalent feature to insure rotational alignment of the multi-core fiber  1222  with the ferrule  1224 . The grooves  1226 ,  1228  and  1230  on multi-core fiber  1222  facilitates the multi-core fiber rotational alignment. 
         [0085]    Therefore, based on the foregoing exemplary embodiments of the invention, an optical interconnect for a multi-core optical fiber with a compact optical transceiver is provided using unique optical elements, thereby leading to improved optical coupling performance, a simpler package and lower cost. 
         [0086]    Although an example of the optical coupling device is shown using a field lens or other substitute for the field lens, it will be appreciated that other optic configurations can be used. Also, although the optical coupling device is useful to provide greater bandwidth in computer systems, it can also be used in audio/visual systems, telecommunications, and other devices or techniques that transmit information over a distance of a first point to a second point. 
         [0087]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.