Abstract:
Methods and tools disclosed herein enable the efficient assembly of a stackable multi-fiber ferrule. The present invention facilitates precisely aligned support members within the stack. In addition, the present invention provides for the consistently high precision repetition of the assembly of stackable multi-fiber ferrules. Thus, stackable multi-fiber ferrules assembled in accordance with the present invention are capable of consistently establishing highly efficient optical connections.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to optical fiber connectors, more particularly, to stackable ferrules for terminating optical fiber ribbons. 
     BACKGROUND OF THE INVENTION 
     Advances in lightwave technology have made optical fiber a very popular medium for large bandwidth applications. In particular, optical technology is being utilized more and more in broadband systems wherein communications between systems take place on high-speed optical channels. As this trend continues to gain more and more momentum, the need for efficient utilization of the precious real estate on circuit boards, racks/shelves, back planes, distribution cabinets, etc., is becoming ever increasingly important. In order to fulfill expectations across the industry, opto-electronic modules and optic fiber devices need to continue to become miniaturized, thereby taking fill advantage of the maturity of micro- and opto-electronic technologies for generating, transporting, managing and delivering broadband services to the ever increasing bandwidth demands of end users at increasingly lower costs. Thus, the industry has placed an emphasis on small form factor optical connectors, such as the LC connector from Lucent Technologies, Inc. However, miniaturization is tempered by the requirements of transmission efficiency. For instance, with the advent of new standards such as gigabit ethernet, wherein the transmission efficiency is becoming more and more critical, the performance of optical connectors is becoming correspondingly important for healthy operation of the system. Thus, it is desirable to obtain component miniaturization without sacrificing transmission efficiency, and sometimes while improving transmission efficiency. 
     With the miniaturization of optical modules and optical fiber devices, the management of optical fiber congestion has become an issue at optical interfaces and connection distribution points. One solution is the use of multi-fiber ribbon in which a plurality of optical fibers are organized and molded side by side in a plastic ribbon. It is known to interconnect these ribbon cables by supporting the fibers between two support members made of a monocrystalline material, such as silicon. In the support members are V-grooves formed utilizing photolithographic masking and etching techniques. The fibers are placed side by side in individual V-grooves of one support member and the other mating support member having corresponding V-grooves is placed over the fibers so as to bind or hold the fibers in a high precision, spatial relationship between the mating V-grooves. The top and bottom support members sandwiching the multi-fiber ribbon are typically bonded together with a clamp or adhesive, forming a ferrule of a multi-fiber connector. Two mating ferrules with the same fiber spacing may then be placed in an abutting relationship so that the ends of the fibers of the respective ferrules are substantially co-axially aligned with one another, thereby forming a multi-fiber connection. If desired, such ferrules can be stacked in order to increase the interconnection density. 
     Multi-fiber ribbons and connectors have numerous applications in optic communication systems. For instance, some opto-electronic and optical application specific integrated circuits (OASIC) devices, e.g, optical switches, optical power splitters/combiners, routers, etc., have several input and/or output ports arranged as linear arrays to which a plurality of fiber are to be coupled. Further, since optical fibers are attached somehow to launch optical signals into these devices and extract optical signals out of these devices, splicing of arrays of fibers (i.e., a multi-fiber ribbon) to such devices can be achieved using multi-fiber connectors. Yet another possible application relates to an optical fan-out fabric where an array of fibers in a multi-fiber ribbon may be broken into simplex or duplex channels for distribution purposes, as is often desired. 
     A critical factor to the optical efficiency of a multi-fiber ferrule, whether or not stacked, is the alignment of the mating ferrules with regard to one another. To that end, alignment pins are often utilized. Alignment pins are received in alignment pin holes or slots in the respective ferrules so as to hold the ferrules in precise alignment with regard to one another. The alignment pins usually extend parallel to the optical fibers, and are preferably made of a material have a similar coefficient of thermal expansion to the ferrules. In one embodiment, as disclosed in U.S. Pat. No. 4,973,127 to Cannon Jr. et al., alignment pin holes are formed by grooves that are laterally disposed on opposite sides of the optical fiber V-grooves in the support members, such that when two support members are brought together, alignment pin holes are defined by mating alignment grooves. In U.S. Pat. No. 5,620,634 to the present inventor, wherein support members are stacked in order to increase the interconnection density, alignment slots are provided on each row of optical fiber, that is, every support member interface. 
     A critical factor to the success of any multi-fiber interconnection system is the ease and speed at which it can be assembled. It is desirable that a ferrule stack be assembled relatively quickly with a minimum amount of effort and overhead so that such connection systems can be manufactured economically. Connection systems which call for elaborate and costly procedures for assembly are not likely to be commercially successful because the cost of manufacturing drives up the price above market. 
     In summary, there continues to be strong market forces driving the miniaturization of fiber optic connection systems, while at the same time demanding that the increasing interconnection density requirements be satisfied. Further, such a connection system should be capable of being manufactured and assembled easily and inexpensively. 
     SUMMARY OF THE INVENTION 
     The present invention comprises methods and tools that enable the efficient assembly of a stackable multi-fiber ferrule. The present invention facilitates the precise alignment of support members within a stackable multi-fiber ferrule. In addition, the present invention provides for the consistently high precision repetition of the assembly of stackable multi-fiber ferrules, and thereby enables the production of consistently highly efficient optical connections. 
     In accordance with an aspect of the present invention, a method for assembling a stackable multi-fiber ferrule utilizing an assembly tool having a slot configured to receive a plurality of v-groove support members therein comprises placing a first support member in the slot of the assembly tool, placing a first stripped multi-fiber ribbon on the first support member so that the individual fibers of the ribbon overlay respective v-grooves of the first support member, applying an adhesive on the first multi-fiber ribbon, and placing a second support member over the first support member within the slot of the assembly tool so as to sandwich the first multi-fiber ribbon, wherein the individual fibers of the multi-fiber ribbon are held between respective v-grooves of the first and second support members, thereby forming a ferrule stack. The method can further comprise the steps of placing a second stripped multi-fiber ribbon on the second support member so that the individual fibers of the ribbon overlay respective v-grooves of the second support member, applying an adhesive on the second multi-fiber ribbon, and placing a third support member over the second support member within the slot of the assembly tool so as to sandwich the second multi-fiber ribbon, wherein the individual fibers of the second stripped multi-fiber ribbon are held between respective v-grooves of the second and third support members. Further steps may include applying an adhesive on the second multi-fiber ribbon, and placing an outer support member over the first inner support member within the slot of the assembly tool so as to sandwich the first multi-fiber ribbon, wherein the individual fibers of the multi-fiber ribbon are held between respective v-grooves of the second and third support members. 
     The method may further comprise applying compressive pressure to the ferrule stack, and applying heat to cure the adhesive. In addition, the method can comprise the step of cleaving off any excess length of the individual fibers extending past a front-end of the ferrule stack. 
     In accordance with another aspect of the present invention, an assembly tool for assembling a stackable multi-fiber ferrule which holds N multi-fiber ribbons between N+1 support members comprises a support body defining a slot, wherein the slot includes a ribbon cavity having a width approximating that of the multi-fiber ribbon and a support member cavity having a profile approximating that of a support member. The assembly tool can comprise a material selected from a group consisting of ceramic, steel, aluminum and plastic. The support member cavity is sized so that a front-end of a support member extends outside the support member cavity. 
     In accordance with yet another aspect of the present invention, a method for assembling a stackable multi-fiber ferrule utilizing an assembly tool having a slot configured to receive a plurality of v-groove support members therein comprises fabricating a plurality of support members, providing an assembly tool, stacking the outer support members and inner support members within the assembly tool which holds the outer and inner support members in registry with one another, wherein multi-fiber ribbons are interposed between adjacent support members, thereby forming a stack, and applying a compressive force to the stack. The step of applying compressive force can comprise applying compressive force while the stack is positioned in the assembly tool. The adhesive can be cured by heating the ferrule. The step of fabricating one support member can include the step of injection molding the support members which, in turn, can comprise providing an injection mold fabricated from a monocrystalline master mold form. 
     Other features and advantages of the present invention will become apparent to one skilled in the art upon examination of the following drawings and detailed description. It is intended that all such features and advantages be included herein within the scope of the present invention as defined by the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a multi-fiber stackable ferrule in accordance with one embodiment of the present invention. 
     FIG. 2A is a top perspective view of an outer support member in accordance with one embodiment of the present invention. 
     FIG. 2B is a bottom perspective view of the outer support member of FIG.  2 A. 
     FIG. 2C is a top perspective view of an inner support member in accordance within embodiment of the present invention. 
     FIG. 2D is a bottom perspective view of the inner support member of FIG.  2 C. 
     FIG. 3 is a front plan view of the multi-fiber stackable ferrule of FIG.  1 . 
     FIGS. 4A-4B are cross-sectional views of a mold utilized for fabricating inner and outer support members of the of the stackable multi-fiber ferrule of FIG.  1 . 
     FIG. 5 is a schematic diagram illustrating the fan-out of multi-fiber ribbon and individual fibers utilizing a stackable multi-fiber ferrule in accordance with an embodiment of the present invention. 
     FIG. 6A is a perspective view of a stackable multi-fiber ferrule assembly tool in accordance with an embodiment of the present invention. 
     FIG. 6B is a top plan view of a stackable multi-fiber ferrule assembly tool of FIG.  6 A. 
     FIG. 7 is a prospective view illustrating support members being loaded into the assembly tool of FIGS. 6A and 6B. 
     FIGS. 8A-8G are top plan views at incremental steps of assembling a stackable multi-fiber ferrule using the assembly tool of FIGS. 6A-6B in accordance with an embodiment of the present invention. 
     FIGS. 9A-9B are flowcharts of the assembly of a stackable multi-fiber ferrule using the assembly tool of FIGS. 6A-6B, as depicted in FIGS. 8A-8G, in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanied drawings, which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numeral refer to like elements throughout. Furthermore, the elements of the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the present invention. 
     With reference to FIG. 1, a multi-fiber stackable ferrule  10  in accordance with an embodiment of the present invention is illustrated. The ferrule  10  comprises two outer support members  12  that sandwich substantially identical inner support members  14 . For purposes of illustrating the present invention, the embodiment chosen terminates five multi-fiber ribbons  16 , though upon reading the disclosure herein, it will be apparent to one of ordinary skill in the art that the present invention may be utilized to terminate any number of multi-fiber ribbons  16 . The support members  12 ,  14  include parallel V-grooves which hold the fibers of the respective multi-fiber ribbons  16  in precise, spaced alignment with respect to one another as the V-grooves of adjacent support members are laid over one another in a mating relationship. Thus, the individual fibers of the multi-fiber ribbons  16  are substantially flush to the front-end face  18  of ferrule  10  so that the fibers may be optically coupled to another ferrule or device. 
     In accordance with one aspect of the present invention, alignment pin holes  20  formed by alignment pin grooves in the support members  12 ,  14  are provided for on every other row of optical fibers, that is, at alternate interfaces of the respective adjacent support members. In particular, the alignment pin grooves of the inner support members  14  are not opposing one another on opposite sides of the inner support member. In the embodiment illustrated, alignment pin grooves are provided in only one surface, though it will be appreciated by those of ordinary skill in the art that alternative designs may be utilized, such as where the alignment pin grooves are diagonal to one another on opposite surfaces. Thus, the inner support members  14  do not have to be thick enough to accommodate two opposing alignment pin grooves, and therefore, can be made thinner than conventional inner support members. Accordingly, the overall height or thickness of the ferrule  10  may be advantageously reduced, and the overall interconnection density increased. 
     With reference to FIGS. 2A and 2B, the inside surface  30  and outside surface  32  of the outer support member  12  are illustrated, respectively. The outer support member  12  includes a front portion  34  and a rear portion  36 . An array of parallel V-grooves  38  for receiving and holding the optical fibers of the multi-fiber ribbon  16  in precise alignment with respect to one another are provided in the front portion  34  of the inside surface  30 . In addition, the inside surface  30  includes relatively deeper V-grooves, referred to hereinafter as alignment pin V-grooves  40 , which are laterally disposed on either side of V-grooves  38  and are sized and shaped for holding alignment pins. While the alignment pin V-grooves  40  extend from the front portion  34  toward the rear portion  36 , it is recognized that the V-grooves  40  may be sized to extend from the front portion  34  to the rear portion  36 , essentially extending from one edge to an opposite edge of inside surface  30 . The lateral space between the V-grooves  38 ,  40  may be defined in accordance with an optical fiber connector interface standard, if desired. Further, while twelve V-grooves  38  are provided by outer support member  12 , it will be appreciated by those of ordinary skill in the art that more or fewer than twelve may be utilized without departing from the present invention. For example, it may be desirable to merely have two V-grooves  38  in a duplex system, or up to 32 V-grooves in other systems. 
     The rear portion  36  includes a ribbon recess  42  which holds a multi-fiber ribbon  16  at or about the point at which the individual optical fibers of the ribbon are separated and stripped. The ribbon recess also provides space for the adhesive utilized to bond adjacent support members together, as discussed below. Further, ribbon recess  42  includes a strain relief element recess  43  for receiving and engaging a lip or other retaining structure at the end of an external strain relief element associated with a multi-fiber ribbon. 
     A retaining pin  44  and a retaining slot  46  are provided on either side of the cable recess  42  for proximately aligning and holding adjacent support members. The retaining pin  44  and slot  46  provide for the lateral alignment of adjacent support members so that corresponding arrays of V-grooves align with one another. The mating V-grooves can be fabricated with such precision, as discussed hereinafter, that the V-grooves themselves precisely align the individual fibers. This is inherent in the V-shaped design which has an acceptance region at the open end or top of each V-groove for receiving an individual optical fiber which is held in a precise predetermined alignment by the sides of the V-groove. The precise alignment of adjacent support members ensures that the mating V-grooves of adjacent support members are in registration with one another. A ridge  48  at the rear portion  36  is provided to register an end-stop in an housing (not shown) in which such ferrules are utilized, as well known in the art. 
     With reference to FIGS. 2C and 2D, opposing first and second surfaces  50 ,  52  of the inner support member  14  are illustrated. The inner support member  12  includes a front portion  54  and a rear portion  56 . A first array of parallel V-grooves  58  are provided in a first surface  50  of the front portion  56  for receiving and holding optical fibers of the multi-fiber ribbon  16 , and relatively deeper alignment pin grooves  60  laterally disposed on either side of the first array of V-grooves  58 . In addition, the second surface  52  of the inner support member  14  includes a second array of parallel V-grooves  62 . Thus, the inner support member  14  includes substantially identical and aligned arrays of V-grooves  58 ,  62  on opposite surfaces for mating with corresponding arrays of V-grooves formed in adjacent support members. In addition, retaining pins  64 ,  66  and retaining slots  68 ,  70  are provided on opposing surfaces  50 ,  52  at the rear portion  58  of the inner support member  14  for aligning and holding adjacent support members, as discussed above with respect to the outer support member  12 . Yet further, a ribbon recess  71  and a strain relief element recess  73  are provided in both surfaces  50 ,  52 , as also discussed above with respect to the outer support member  12 . 
     In accordance with the present invention, the inner support member  14  does not include opposing alignment pin grooves in opposite surfaces. Specifically, with reference to the embodiment illustrated in FIGS. 2C and 2D, the second surface  52  does not include alignment pin V-grooves. It is noted, however, that the second surface may include alignment pin grooves which are staggered (ie., offset) with respect to the corresponding alignment pin grooves  60  in the first surface  50  in the alternative. However, if staggered alignment pin grooves are utilized, then the lateral space on either side of the arrays of V-grooves may have to be increased, which may not be acceptable in certain applications. Thus, whether one surface does not include alignment pin grooves or staggered alignment pin grooves on opposite surfaces, the thickness of the inner support member may be less than that of conventional support members since the support member does not have to be thick enough to accommodate opposing alignment pin grooves. For example, with reference to FIG. 3, the thickness  72  of an inner support member is approximately 740 microns in the preferred embodiment, whereas conventional support members are often 2500 microns thick. Accordingly, by reducing the thickness of the inner support member, more multi-fiber ribbons can be terminated with a ferrule of the same size, thereby enabling the increase of interconnection density. 
     In addition, it is preferred that the thickness  72  of the inner support members should be such that the distance  74  between the centers of adjacent V-grooves within an array is a whole number multiple of the distance  76  between the center of the V-grooves at one interface and the centers of the V-grooves at an adjacent interface, or vice versa. Accordingly, the thickness  72  is approximately 740 microns and the spacing at the interfaces  75  between adjacent support members is approximately 10 microns, thereby resulting in a distance  76  that is approximately 750 microns, which is a multiple of an illustrative fiber to fiber distance  74  of 250 microns. The approximate distance of 10 microns between adjacent support members is by design so that when two mating support members are placed about a multi-fiber ribbon, the fiber will be under compression. This ensures that fibers with nominal variances in their outside diameters are precisely aligned between mating V-grooves. The controlling V-groove is preferably controlled by an applicable interconnection interface standard. For purposes of this disclosure, the center of a V-groove is the center of an optical fiber held in the V-groove. Thus, greater flexibility with regard to whether the interface planes of a stackable ferrule are parallel or perpendicular to the interfaces of a connecting ferrule. 
     Thus, by flipping the face-down side of each successive inner support member  14  added to a ferrule stack, the alignment pin holes  20  formed by the alignment pin grooves are positioned at alternating interfaces  75 , also referred to as rows of optical fibers, as illustrated in FIGS. 1 and 3. In order to adequately align and secure the ferrule  10  from moving with respect to another ferrule to which it is being optically coupled, there should be at least two alignment pins. While the present invention does not necessarily provide for two alignment holes on every row of optical fibers, it does provide a more than adequate precision and rigidity for most applications, while permitting the overall thickness of the stack of ferrules to be reduced relative to conventional designs. 
     Accordingly, a ferrule  10  in accordance with the present invention may terminate a theoretically infinite number of multi-fiber ribbons by the present invention utilizing two outer support members  12  and an appropriate number of inner support members  14 . As only the two structural components are necessary, the overall costs of a stackable multi-fiber ferrule in accordance with the present invention can be less than that of comparable stackable ferrules that require more than two components. This is, at least in part, because the support members can be fabricated using plastic injection molding techniques with only two molds: one for the outer support member  12  and one for the inner support member  14 . This further increases the precision of the V-grooves because adjacent parts will often be formed from the same mold. 
     In particular, the support members  12 ,  14  are preferably fabricated using the techniques described in U.S. Pat. Nos. 5,388,174; 5,620,634 and 5,603,870, the disclosures of which are incorporated here by reference as if set forth in full. This process has been proven to consistently and reliably produce features with accuracy on the order of 1 μm or better. Generally, this process is as follows. Initially, a monocrystalline body, such as a silicon chip, is anisotropically etched using conventional masking and etching techniques to produce V-grooves. For example, either KOH/water or EDP/water solutions may be used as an etchant. The etch rate of the silicon may be several orders of magnitude greater than that of the mask layer such that the unmasked portions are etched away when exposed to the etchant solution, thereby defining the V-grooves along the {111} crystal planes of the silicon. By precisely controlling the mask pattern and the etching process, precise V-grooves of predetermined spacing, widths, and depths may be fabricated in the silicon wafer. It is noted that the V-grooves do not have to be exactly V-shaped. For example, since the optical fibers and alignment pins are essentially round in cross-section, the bottom of the V may be truncated in the same fashion as the alignment pin grooves  40 ,  60 . If truncated, the grooves  40 ,  60  should be deep enough to provide adequate clearance for an alignment pin. Past that depth, the bottom of the groove is essentially non-functional. However, the depth of the groove may be limited by the necessary structural strength required of the support member, and in particular, the portion of the support member defining the alignment pin groove. 
     To allow for shrinkage of the plastic during the subsequent molding process, the features on the silicone chip, such as the V-grooves and their spacing, should be made somewhat larger than is finally intended for the final support member. A thin metal layer is then electro-formed over the V-grooves; thereafter, the silicon body is removed or destroyed, as by etching it in, for example, a mixture of HF, HNO 3  and water, or KOH and water (or other known etchants of silicon) suitable for use herein. In the preferred embodiment, the metal layer is formed by electroplating nickel over the silicon wafer. Nickel is preferred because it can be conveniently electro-formed with reasonable hardness (e.g., ˜50 Rockwell). The electro-formed metal layer forms an inverse replica of the silicon wafer chip which is machined for used as an insert in an injection mold for defining the V-grooves, as well as other features, of the support members  12 ,  14 . 
     Experiments are then conducted with the injection mold to optimize molding conditions. This involves selection of the most suitable molding compound, molding parameters that produce a smooth surface morphology, and most importantly the degree of mold shrinkage. Such experiments help determine the operation parameters for the optimal output. Preferred material for forming the support members is polyphenylene sulfide (PPS), which has a shrinkage of ˜0.4% below the dimensions of the original silicon master. Consequently, the dimensions of the silicon master should be ˜0.4% greater than the final desired dimensions. For bonding the support members  12 ,  14  together, any of various optical adhesives can be used, such as Epo-Tek 353ND, which is commercially available from Epoxy Technologies, Inc., Billerica, Mass. 
     Using an injection mold  78 , as depicted in FIG. 4A, an inner support member  14  in accordance with an embodiment of the present invention can be formed. The injection mold  78  includes a first part  79  for forming the features of the first surface  50  and a second part  80  for forming the features of the second surface  52 . It is noted that the corresponding V-grooves of the first part  79  and the second part  80  are precisely aligned with one another. Likewise, an injection mold  81 , as depicted in FIG. 4B, may be utilized to form the outer support member  12 . The injection mold  78  includes the first part  79  for forming the features of the inside surface  30  and a third part  82  for forming the features of the outside surface  32 . Accordingly, support members  12 ,  14  can be formed sharing mold part  79 , thereby comprising a three-part mold construction. By only requiring three parts to mold the inner and outer support members  12 ,  14 , the cost of manufacturing and the resulting precision of the molded parts may be increased. Preferably, experiments are initially conducted to optimize molding conditions. This involves selection of the most suitable molding compound, molding parameters that produce and smooth surface morphology, and most importantly the value of mold shrinkage. Such experiments help determine the operation parameters for the optimal output. 
     With reference to FIG. 5, an exemplary application is provided for a stackable multi-fiber ferrule  10  in accordance with an embodiment of the present invention at a distribution point in which the multi-fiber ribbons  16  terminate at the ferrule  10  and fan-out into two single ribbon ferrules  110 ,  210  and a three ribbon ferrule  310 . The fiber terminations may be coupled to independent optical circuits, to a single broad optical source that illuminates all the fibers, or may be selectively tapped off as in a switch or distribution point. Further, the one ribbon ferrule  110  can be mated to another one ribbon ferrule  410 , which may itself terminate one or more individual optical fibers  116 . The optical fiber(s)  116  may then fan-out to a plurality of single or multi-fiber ferrules  510 . Thus, the optical fiber(s)  116  may be a single optical fiber or multiples thereof. However, this is merely one illustrative embodiment which shows several of the possible fan-out combinations which may be efficiently achieved by a stackable ferrule in with the present invention. 
     In yet another application, because of the increased connection density and precise fiber alignment of a stackable multi-fiber ferrule assembled in accordance with an embodiment of the present invention, the stackable multi-fiber ferrule may be suitable for mounting at its face-end to an array of precisely aligned surface emitting/receiving devices such as surface emitting lasers (SEL) or other discrete components that can be fabricated with precise spacing on a circuit board or substrate. The optical fibers terminating with the stackable multi-fiber ferrule can be coupled to the surface device whereby a single component is placed in a butting relationship with each optical fiber. Thus, a low profile device connection can be achieved. 
     With reference now to FIGS. 6A-6B, an assembly tool  84  in accordance with an embodiment of the present invention is illustrated. The assembly tool is sized and shaped to receive two or more support members  12 ,  14  with precise alignment for assembling a multi-fiber stack, as illustrated in FIG.  1 . The assembly tool  84  comprises a support body  86  which for purposes of the present embodiment is substantially rectangular. The support body  86  defines a slot  88  having a ribbon cavity  90  and a support member cavity  92 . The support cavity  92  has a widened width portion  94  for receiving the rear portions  36 ,  56  of the support members  12 ,  14 , respectively and a non-widened width portion  95  for receiving the front portions of the support members. 
     The assembly tool is preferably machined out of a metallic material such as steel or aluminum, though it will be recognized that there are numerous suitable materials and methods for fabricating the assembly tool, such as cast metal, machined metal, or molded plastic. The height H of the slot  88  can be designed to accommodate a predetermined number of support members. The length L of the support member cavity  92  is preferably designed to be less than the corresponding length of the support members  12 ,  14  so that a portion of the front portions  34 ,  546  extend outside the support member cavity  92 , as illustrated in at least FIG.  7 . Thus, support members  12 ,  14  may be positioned in the assembly tool  84  with high precision with respect to one another, as shown in FIG.  7 . It is further noted, however, that the length L of the support cavity  92  may be greater than the corresponding length of the support members  12 ,  14  if desired, though in such cases it is preferred that a longitudinal section of the lower portion of the support cavity  94  be cut out such as that defined by phantom lines  96  of FIG. 6B, so that a clamping or compression device can be placed about the front portion of the stackable multi-fiber ferrule, at the front-end face  18 , as discussed below. 
     A method and corresponding sequence of events comprising an embodiment of the present invention is provided for by FIGS. 8A-8G and the flowchart of FIGS. 9A and 9B. Initially, the various components, including an assembly tool  84 , an outer support member  12 , and a multi-fiber ribbon  16 , are collected and then prepared. This preparation includes stripping back the coating on the multi-fiber ribbon  16  at an end so as to expose end portions  98  of the individual optical fibers of the multi-fiber ribbon  16 , as illustrated in FIG.  8 A. While not required, it is preferred that the coating on the fibers be removed because the coatings are not dependably uniform in thickness, that is, the optic fiber may be somewhat off-center with respect to the center of the coated fiber, which may prevent proper alignment to an abutting fiber. 
     The outer support member  12  is then placed in the support member cavity  92  of the assembly tool  84 , as illustrated in FIG.  8 B. The multi-fiber ribbon  16  is then placed over the outer support member  12  so that the individual fibers thereof are aligned with the V-grooves  38  of the outer support member  12 , as illustrated in FIG.  8 C. Note that the end portions  98  of the individual fibers extend past the front-end of the support member  12  so that the front-end of the stack can be polished until the fibers are substantially flush with the front-end of the support members comprising the stack. Thus, the multi-fiber ribbon should be stripped back a length sufficient to ensure that a portion of the ends of the fibers extending past the front-end of the support plate  12  have been stripped. 
     An adhesive, such as Epotek 353ND, is then applied to the stripped fibers and the coated portion of the multi-fiber ribbon  16  to bond adjacent support members sandwiching the optical fibers to one another so as to securely hold the optical fibers in place. 
     An inner support member  14  is then placed over the stripped multi-fiber ribbon  16  and the outer support member  12 , as illustrated in FIG.  8 D. The assembly tool  84  maintains the support members  12  and  14  in precise alignment with respect to one another so that the mating V-grooves of the respective support members are in registration with one another. Thus, each optical fiber is contained by mating V-grooves of the respective support members in precise alignment with regard to one another. This is important in order that the optical fibers are precisely positioned so that they can be efficiently coupled to an abutting optical fiber of a mating ferrule. 
     The next multi-fiber ribbon  16  can then be added to the stack, as illustrated in FIG. 8E as can successive inner support members in the manner described above. The stack can be built to a desired number of multi-fiber ribbons by repeating the steps above. The last support member placed on the stack is a second outer member  12 , as illustrated in FIG.  8 F. While in the assembly tool  84 , the multi-fiber ferrule  10  is clamped, preferably at the front portions  34 ,  54  of the support members  12 ,  14 , that is, the portion of the support members  12 ,  14  extending outside the support body  86 , so that compressive forces are applied to the stack  10 , such as by a calibrated clip or vice. Preferably, approximately 10 lbs. force is applied in the embodiment disclosed herein, though the amount of pressure may vary based on the adhesive, the design of the support members, the size of the stack, etc. The multi-fiber ferrule is then removed from the assembly tool  84  and placed in an oven for curing the adhesive. In the present embodiment, the adhesive can be cure at 85° C. for approximately 15 minutes. Once the adhesive has cured, the end portions  98  of the optical fibers are cleaved and the front-end of the multi-fiber ferrule  10  is polished, as illustrated in FIG.  8 G. 
     With reference now to FIG. 9, a illustrative embodiment of the present invention is provided. Initially, the bottom outer support member is placed within the assembly tool  84 , as indicated by block  101 . A first stripped multi-fiber ribbon fiber is place on the bottom outer support member, as indicated by block  103 , and adhesive epoxy is applied to the stripped fibers, preferably covering a portion of each fiber and contacting the end of the plastic coating of the multi-fiber ribbon, as indicated by block  105 . Next, an inner support member is placed over the stripped multi-fiber ribbon and the outer support member so that the v-grooves of the outer and inner support members align in precise registration, as indicated by block  107 . A second stripped multi-fiber is placed on the inner support member, as indicated by block  109 , and adhesive epoxy is applied at front ends of the stripped fibers, preferably covering a portion of each fiber and contacting the end of the plastic coating of the multi-fiber ribbon, as indicated by block  111 . 
     It is then determined at block  113  whether or not there are any more multi-fiber ribbons to add to the stack. If there are more ribbons to add, then the steps of blocks  107 - 111  are repeated. If not, then a top outer member is placed over the last multi-fiber ribbon and inner member within the assembly tool, as indicated by block  115  of FIG. 9B. A pressure clamp is attached to the front-end of the ferrule stack, and the clamped stack is removed from the assembly tool, as indicated by block  117 . At block  119 , the epoxy in the stack is cured under heat and pressure. The excess fiber length extending beyond the front-end of the ferrule stack is cleaved and the front-end is polished, if desired, as indicated by block  121 . 
     The assembly tool and associated assembly method of the present invention therefore facilitates the precise alignment of the plurality of inner and outer members that must be assembled to form the multi-fiber ferrule of the present invention. In particular, the assembly tool and associated method allows for the plurality of inner and outer members to be assembled in an efficient and repeatable manner without requiring costly fixtures or procedures. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.