Abstract:
A coupler adapter has a base and at least one alignment feature disposed upon the base. The at least one alignment feature is constructed for aligning a multi-fiber bundle to an opto-electronic module to permit transmission of optical signals between the multi-fiber bundle and optical devices within the opto-electronic module when the the opto-electronic module is larger in span than a spacing of alignment elements used in a commercial connector that holds the multi-fiber bundle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority under 35 USC 119(e)(1) of U.S. Provisional Patent Application Serial No. 60/302,240 filed Jun. 29, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to connectors and, more particularly, to connectors used in fiber optic communication arrangements.  
         BACKGROUND  
         [0003]    Connectors to attach pieces to an opto-electronic module exist, but in all cases, the size of the opto-electronic part chip in the module is smaller than the spacing between the alignment elements, for example, the guide pins used to ensure accurate, reproducible alignment between fibers in the connector and the module.  
           [0004]    This prior art arrangement is shown in FIG. 1. A fiber bundle is terminated into a connector which contains a ferrule. The Connector-Ferrule combination performs two functions: It holds the individual fibers very accurately with respect to one another and it holds the multiple fibers, as a group, very accurately with respect to the particular alignment features so that when the connector is plugged into a mating connector (holding additional fibers or on a module), the two connectors align the fibers that are integrated with the first connector with the corresponding features (either fibers or optical or mechanical devices) that are integrated into the second connector.  
           [0005]    In order to maintain high accuracy when plugging two connectors together, there are usually two or more alignment features that are spaced apart over some distance. However, to maintain the accuracy of these alignment features with respect to one another, they cannot be separated in space by too great a distance. This is because, when manufacturing parts with extreme accuracy, the manufacturing error in relative placement of the alignment features increases as those features get spaced further apart. Hence, the features need to be spaced far enough that they can control such things as X-Y positioning and rotation in that plane accurately enough, but not so far apart that the accuracy of the placement of those features themselves interfere with the accuracy of the connection.  
           [0006]    For purposes of compatibility, the industry currently uses a few standard connectors, for example the MTP® connector (a registered trademark of US Conec Ltd). The MTP connector has two alignment or guide pins spaced 4.6 mm apart. As a result, the size of an opto-electronic part that can be used with this connector is limited by the spacing of the alignment or guide pins.  
           [0007]    As time progresses, opto-electronic components or modules have begun to incorporate chips into having more and more optical devices and, in some cases, greater electronic functionality. However, as the numbers of devices and functionality increase, the chips get larger. Thus, the connector can become a limitation on the size of the chip (and hence the number of devices or amount of functionality).  
           [0008]    Compounding the problem is the fact that, in modules currently available, the alignment features on the module side are integrated into the module package.  
           [0009]    Presently, opto-electronic chips are or will imminently be larger than the spacing of the alignment features on the optical connector. Thus, as shown in FIG. 2, there is a problem with providing alignment features on the module side that meet the spacing criteria necessary to connect to currently available commercial connectors.  
           [0010]    One possible solution to the problem is to design a wholly new connector for use with larger chips. However, connector design is expensive and typically outside the business areas of producers of the chips. Moreover, there is no way to guarantee widespread acceptance of such a connector, thereby limiting the market for both the chips and connectors. In addition, it is desirable for such larger chips to nevertheless be compatible with existing connectors, to avoid the problem of widespread rejection due to the inherent obsolescence effect it will have on existing products already in use.  
           [0011]    Thus, there is a need for a way for chips larger than the alignment pin spacing to be able to be used with current commercially available connectors.  
         SUMMARY OF THE INVENTION  
         [0012]    We have developed a mechanical connector piece which provides a way to attach a multi-fiber connector to an opto-electronic module when the size of the opto-electronic component (i.e. chip) for the module is larger in a real extent than the spacing of the high precision alignment elements (e.g. guide pins or other alignment features) used in commercial connectors.  
           [0013]    The advantages and features described herein are a few of the many advantages and features available from representative embodiments and are presented only to assist in understanding the invention. It should be understood that they are not to be considered limitations on the invention as defined by the claims, or limitations on equivalents to the claims. For instance, some of these advantages are mutually contradictory, in that they cannot be simultaneously present in a single embodiment. Similarly, some advantages are applicable to one aspect of the invention, and inapplicable to others. Thus, this summary of features and advantages should not be considered dispositive in determining equivalence. Additional features and advantages of the invention will become apparent in the following description, from the drawings, and from the claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 shows a connector and module according to the prior art;  
         [0015]    [0015]FIG. 2 shows the problem that will be encountered when a commercial connector needs to be connected on a module having a chip with a larger area than the spacing of the alignment features of the connector;  
         [0016]    [0016]FIG. 3 illustrates a coupler adapter with alignment features placed on optical components and configured to mate with a commercial optical fiber holding the connector;  
         [0017]    [0017]FIG. 4 shows the alignment features of FIG. 3 integrated with the module package;  
         [0018]    [0018]FIG. 5 illustrates the alignment features of FIG. 4 with the addition of stop; and  
         [0019]    [0019]FIG. 6 shows an exploded view of a variant of the coupler adapter in FIG. 3.  
     
    
     DETAILED DESCRIPTION  
       [0020]    We have created different variants of a connector usable to attach a fiber bundle in a commercially available connector to an opto-electronic module with high, reproducible accuracy. The connector may be one designed to allow the fiber bundle to be ‘plugged-in’ just once or could be removable style which could be ‘plugged-in’ and removed multiple times. A few examples of such known cable styles are the MTP, MPO, MPX, SMC, ST, LC, MT-RJ. While an apparatus constructed according to the teachings herein could be used with any opto-electronic module or connector for such applications, it is particular useful for opto-electronic modules where the chips to which the fibers in a fiber bundle must be mated are larger in lateral and/or vertical extent in a plane containing the spacing features, for example, in the case of guide pins the axes of the guide pins, than the spacing of the alignment features themselves.  
         [0021]    Adverting to FIG. 1, optical components  110  of a module package  100  are smaller than the spacing of male alignment features  120  and female alignment features  130 . Shown is a prior art arrangement that includes a fiber bundle  150  terminated into a connector  140  which contains a ferrule. In this prior art arrangement, the Connector-Ferrule combination holds individual fibers very accurately with respect to one another and it holds the multiple fibers, as a group, very accurately with respect to the particular alignment features so that when the connector  140  is plugged into a module package  100  having optical components  110 , the two connectors align the fibers that are integrated with the first connector with the corresponding features (either fibers or optical or mechanical devices) that are integrated into the module package  100 . The module package  100  further include the male alignment features  120  and female alignment features  130  to assist in aligning the fibers. However, in this arrangement there is no interference with the alignment features since the optical components  110  are smaller than the spacing between the alignment features.  
         [0022]    [0022]FIG. 2 shows the problem encountered when a commercial connector  230  holding fiber bundle  240  needs to be connected on a module  200  that has a chip or optical components  210  with a larger area than the spacing of alignment features  220  of the connector  230 .  
         [0023]    We have devised at least three approaches that overcome the problem noted above. Moreover, we have recognized that using certain variants of our approaches in some applications will introduce other problems previously unrecognized. However, we have devised other variants which overcome those problems and provide further advantages.  
         [0024]    In one example approach in accordance with the teachings of the invention, shown in FIG. 3, we create a coupler adapter  320  that can be placed on top of the optical components  310  of a module package  300  and is configured to mate with a commercial optical fiber holding connector  330  that holds fiber bundle  340 . The coupler adapter  320  is designed in such a way that it has alignment features  324  built into it and is constructed to have holes or an optical access window  322  through it that allow optical access to the underlying optical devices. In addition, the coupler adapter  320  may include a base  328 , and a securing means  326  generally used in the industry to hold the base to the optical components  310  or the module  300 . The optical components  310  and the coupler adapter  320  are designed together in such a way that the portions of the coupler adapter  320  that do not allow light to pass through do not impact the operation of the chip and/or the performance of the module as a whole. This allows use of alignment features  324  and alignment features  332  of connector  330  spaced in a format compatible with high precision connectors while still allowing the optical components to be of an arbitrarily large size.  
         [0025]    Alternative variants use a simpler approach, such as shown in FIG. 4, that has a substantially lower yield but allows for continuing the practice of having alignment features integrated with a module package  400 . In these variants, the chips or optical components  420  are designed so that no components are located at the locations of the alignment features  432  for an area slightly larger than the cross section of the alignment features  432  of connector  430  holding fiber bundles  440 . Holes  422  are then etched through the chips or optical components  420  to allow pins  410  to protrude through.  
         [0026]    A third option is similar to the first approach except, with the first approach it is possible for the adapter to flex and/or something on the connector to protrude such that something on the inserted connector can potentially impact the devices on the chip in some applications. Thus, the third approach incorporates stops  512  on pins  510  that mate with the alignment features  532  having recess  534  to prevent the connector  530  that holds fiber bundle  540  from being inserted to far. The module package  500  further includes optical components  520  having through holes  522  in the optical components  520 .  
         [0027]    One advantage of the first and third approach is that forces incurred by the module as a result of the insertion of the connector will be applied to the module via the adapter. Thus, they will be distributed over a larger area and hence produce less mechanical stress on the module.  
         [0028]    [0028]FIG. 6 shows a further variant in accordance with the invention in exploded view. As shown in FIG. 6, a complex coupler adapter  620  (having a window  624 ) that is capable of:  
         [0029]    being attached to an optical component module  610 ,  
         [0030]    containing the alignment features required for high accuracy and for coupling to a fiber bundle  640 ,  
         [0031]    being fused with a coupling element  650  into which a fiber bundle connector  630  would fit, and  
         [0032]    allowing all of the optical signals from the fiber bundle  640  to interact with all of the optical devices on the optical chip.  
         [0033]    As noted above, the coupler adapter  620  piece can be readily made compatible with commercial connectors. As shown, the variant of FIG. 6 is compatible with an MTP-style connector system. It is designed to be ultrasonically welded to the coupler piece of an MTP connector system. It also connects to a ferrule which has either guide pin holes or the pins themselves. That is, it can be readily made with pins  624  included (male), such as shown, or with holes  625  (female). The two configurations allow either style of pin-configured fiber bundles to be used with our coupler adapter. The coupler adapter further may have secondary pins  626  to further assist in the alignment of the fiber bundles.  
         [0034]    It should therefore be understood that the above description is only representative of illustrative embodiments. For the convenience of the reader, the above description has focused on a representative sample of all possible embodiments, a sample that teaches the principles of the invention. The description has not attempted to exhaustively enumerate all possible variations. That alternate embodiments may not have been presented for a specific portion of the invention, or that further undescribed alternate embodiments may be available for a portion, is not to be considered a disclaimer of those alternate embodiments. One of ordinary skill will appreciate that many of those undescribed embodiments incorporate the same principles of the invention and others are equivalent.