Patent Publication Number: US-2023161113-A1

Title: Field Changeable Fiber Optic Connector Polarity Keying

Description:
REFERENCE TO RELATED CASES 
     This application claims priority under 35 U.S.C. § 119 (e) to provisional application No. 62/269,946 filed on Dec. 19, 2015, and to provisional application No. 62/599,311 filed on Dec. 15, 2017, and under 35 U.S.C. § 120 to U.S. patent application Ser. No. 15/383,881, filed Dec. 19, 2016, and to U.S. patent application Ser. No. 15/881,866, filed Jan. 29, 2018, and to U.S. patent application Ser. No. 16/164,382, filed on Oct. 18, 2018, and to U.S. patent application Ser. No. 16/221,875, filed on Dec. 17, 2018, to U.S. patent application Ser. No. 16/927,784, filed on Jul. 13, 2020, and to U.S. patent application Ser. No. 17/502,112, filed on Oct. 15, 2021, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Fiber optic jumper cables are used to connect various pieces of telecommunications equipment. These fiber optic jumper cables typically have 12 or more optical fibers in them and are terminated using fiber optic ferrules. The fiber optic jumper cables are either plugged directly into telecommunications equipment (e.g., a transceiver, etc.) or are connected to another fiber optic jumper cable by use of an adapter. Since the fiber optic jumper cables have a number of optical fibers, the routing of those optical fibers is important to ensure that signals traveling on the optical fibers reach the intended destination and in the correct position in the telecommunications equipment or the other fiber optic jumper cable. Thus, the fiber optic jumper cables have a polarity, which is dictated by the positioning of the optical fibers secured in the fiber optic ferrules. Each of the fiber optic ferrules has a particular orientation, and the relationship of the position of the optical fibers to the fiber optic ferrule determines the polarity. However, there are times that the polarity of the fiber optic connector needs to be changed in the field due to changes in the routing, equipment, or design, or simply because the customer ordered the incorrect polarity. However, changing the polarity in the field would require that the connector housing be changed, while the optical fibers are attached. This is tricky, time consuming, and, most importantly, may damage the connector, the optical fibers or the entire fiber optic jumper cable. 
     Thus, a fiber optic connector that allows for the polarity to be changed in the field without removing any of other components of the fiber optic connector is needed. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to fiber optic connector that includes an inner connector housing, the inner connecting housing having a top portion and a bottom portion connected by two side portions, an outer connector housing surrounding at least a portion of the inner connector housing, a key disposed in a recessed portion of the inner housing, the key having a cantilevered portion extending from a central portion towards a front end thereof, a first latch disposed on the cantilevered portion and having a surface facing a rear end of the key to engage a forward facing surface in one portion of the fiber optic connector housing to prevent the key from moving rearwardly upon application of a rearward force to the key. 
     In some embodiments, there are first and second portions extending along of a portion of the cantilevered portion on opposite sides thereof. 
     In some other embodiments, front end of the key has a wall in front of the cantilevered portion to guard the first latch. 
     In another embodiment, a key to be disposed in a portion of a fiber optic connector housing that includes a main body extending between a front end and a rear end, a cantilevered portion extending from a central portion of the main body towards the front end, first and second portions extending along of a portion of the cantilevered portion on opposite sides thereof, and a first latch on the cantilevered portion and having a surface facing the rear end of the key and to engage a forward facing surface in the portion of the fiber optic connector housing to prevent the key from moving rearwardly upon application of a rearward force to the key. 
     In yet another embodiment, there is a key to be disposed in a portion of a housing of a fiber optic connector that includes a main body extending between a front end and a rear end; and a cantilevered portion extending from a central portion of the main body towards the front end and having a latch thereupon, the cantilevered portion being in a relaxed first state in a first position in an adapter and being in a compressed second state when in a second position in the adapter. 
     According to another aspect of the present invention, there is a fiber optic connector that includes a fiber optic ferrule, an inner connector housing surrounding at least a portion of the fiber optic ferrule, the inner connecting housing having a top portion and a bottom portion connected by two side portions, the top and bottom portions having an outer surface and a thickness, an outer connector housing surrounding at least a portion of the inner connector housing, the outer connector housing movable relative to the inner connector housing, a top recessed portion on the top portion of the inner connector housing, the top recessed portion extending into the thickness of the top portion, a bottom recessed portion on the bottom portion of the inner connector housing, the bottom recessed portion extending into the thickness of the bottom portion, a forward facing surface and a rearward facing surface disposed in each of the top and bottom recessed portions, and a first key to be disposed within the top recessed portion and a second key disposed within the bottom recessed portion, each of the first and second keys having a first latch to engage the forward facing surface in a first position and a second latch to engage the rearward facing surface to prevent removal of the first and second keys from the fiber optic connector. 
     It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description, serve to explain the principles and operations of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a planar view of a Type A jumper; 
         FIG.  2    is a planar view of a Type B jumper; 
         FIG.  3    illustrates a connectivity method for using Type A adapters; 
         FIG.  4    illustrates a connectivity method for using Type B adapters; 
         FIG.  5    illustrates the Type A adapters; 
         FIG.  6    illustrates the Type B adapters; 
         FIG.  7    is a partial cross section view of one embodiment of the fiber optic connector having two keys according to the present invention; 
         FIG.  8    is a perspective view of one embodiment of a key according to the present invention and a cross section of that key; 
         FIG.  9    is a front perspective view of one embodiment of an inner connector housing according to the present invention showing the top of the inner connector housing (the bottom side being the same); 
         FIG.  10    is a cross sectional view of the inner connector housing of  FIG.  9    and two keys according to  FIG.  8    in a first position and a second position; 
         FIG.  11    is a perspective view of one embodiment of a tool to be used with the fiber optic connector of  FIG.  7   ; 
         FIG.  12    is a perspective view of the tool in  FIG.  11    from the opposite side; 
         FIG.  13    is a cross section along a longitudinal axis of the tool in  FIG.  11   ; 
         FIG.  14    is a partial cross section of the fiber optic connector with the tool in a starting position on the fiber optic connector; 
         FIG.  15    is a detail view of the chamfered leading edge of the tool of  FIGS.  11 - 13    engaging one key to reverse polarity of the fiber optic connector; 
         FIG.  16    is a partial cross section of the fiber optic connector with two detail drawings showing the first key in the second position with a first latch in the indentation and the rearward end of the key against the key stop; 
         FIG.  17    is a cross section of the fiber optic connector with the tool engaging the second of the two keys to pull the second key forward; 
         FIG.  18    is a partial underside view of the protrusions of the tool engaging the second key as illustrated in  FIG.  17   ; 
         FIG.  19    is an underside view of the tool, key and inner connector housing showing the second key in the first position after the tool is pulled forward; 
         FIG.  20    is a cross section view of the fiber optic connector illustrating the first key in the second position and the second key in the first position as also illustrated in  FIG.  19   , thus reversing the polarity of the fiber optic connector; 
         FIG.  21    is an enlarged, partial cross-section view of one of the keys in  FIGS.  8  and  10   ; 
         FIG.  22    illustrates the forces on the key illustrated in  FIG.  21    when the key engages a fiber-optic connector adapter in an incorrect orientation; 
         FIG.  23    illustrates the stresses, compression and deformation the latch and inner connector housing in  FIG.  22    experience when the key is subjected to a rearward directed force; 
         FIG.  24    is a perspective view of an embodiment of a key to be disposed in a portion of a fiber optic connector housing according to the present invention; 
         FIG.  25    is a bottom perspective view of a cross section of the key in  FIG.  24   ; 
         FIG.  26    is a front elevation view of the key in  FIG.  24   ; 
         FIG.  27    is a cross-section view of an inner connector housing and two keys from  FIG.  24   ; 
         FIG.  28    is an enlarged portion of the inner connector housing and key in  FIG.  27   ; 
         FIG.  29    is an enlarged portion of the fiber optic connector and key in  FIG.  24   ; 
         FIG.  30    illustrates the stresses, compression and deformation the latch in  FIG.  24    experiences when the key is subjected to a rearward directed force; 
         FIG.  31    is a perspective view of another embodiment of a key to be disposed in a portion of a fiber optic connector housing according to the present invention; 
         FIG.  32    is a cross section of a portion of the key in  FIG.  31    illustrating a front wall engaging a portion of the key when a rearward directed force is applied thereto; 
         FIG.  33    is bottom elevation view of the key in  FIG.  31   ; 
         FIG.  34    is a perspective view of another embodiment of a key to be disposed in a portion of a fiber optic connector housing according to the present invention; 
         FIG.  35    is a cross section of a portion of the key in  FIG.  4    illustrating a front wall engaging a portion of the key when a rearward directed force is applied thereto; 
         FIG.  36    is top elevation view of a portion of the key in  FIG.  34   ; 
         FIG.  37    is a perspective view of another embodiment of a key to be disposed in a portion of a fiber optic connector housing according to the present invention; 
         FIG.  38    is a cross section of a portion of the key in  FIG.  37    illustrating a front wall before a rearward directed force is applied thereto; and 
         FIG.  39    is a cross section of a portion of the key in  FIG.  37    illustrating a front wall after a rearward directed force is applied thereto. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiment(s) of the invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. the optical paths that are required when ordering the fiber optic jumper cables. 
     Further to the above discussion, illustrated in  FIGS.  1 - 6    are components of a fiber optic jumper cable, the adapters and routing pattern of the optical fibers. There are two types of fiber optic jumper cables, which are illustrated in  FIGS.  1  and  2   . In  FIG.  1    is a Type A fiber optic jumper cable  10  while  FIG.  2    is a Type B fiber optic jumper cable  12 . In a Type A fiber optic jumper cable, the optical fibers are in the same position at both ends (as one looks at the end of the fiber optic ferrule with the keys  14 , in the same direction). It should be noted that with the keys up at both ends in a Type A fiber optic jumper cable, the fibers are crossed over the length of the jumper. If the keys were opposite (one of the keys not pointing up, but rather down into the page, then the optical fibers would appear to run straight from one end to the other). In a Type B fiber optic jumper cable, the optical fibers are reversed. For example, the optical fiber in position  1  in one fiber optic ferrule is in position  12  of the fiber optic ferrule at the other end. As a result, the person designing the system needs to be aware of the optical paths that are required when ordering the fiber optic jumper cables. 
     As an example,  FIG.  3    illustrates a system  16  that uses an A-type connectivity system. The uncoupled ends of the fiber optic jumper cables illustrated on the left side are to be mated with a transceiver (not shown). As is known in the art, there are positions for transmitting signals (Tx) and receiving signals (Rx). It is important that the fiber optic jumper cables  10 , 12  are designed so that the transmit position in one of the transceivers is mated with a receive position in the other. One optical path  18  is illustrated by the solid line around the system  16 . The transmit position on the bottom transceiver (at position  1 ) needs to reach the receive position  1  on the transceiver at the top. So, with the optical fibers  20  being all parallel to one another, there are two Type A fiber optic jumper cables and one Type B fiber optic jumper cable required to achieve that result. As illustrated in middle of the system  16 , a Type A adapter  22 —to join the ends of the fiber optic jumper cables—is used and the illustration shows the configuration from both ends. So, the Type A adapter has one side with the key up and the other side with the key down. See also  FIG.  5   . Thus, if one type A and two type B fiber optic jumper cables are ordered, then the system  16  will not work. It would be better if the key at one end of the fiber optic jumper cables could be changed (or if the keys can be easily changed, then only one type of jumper needs to be ordered and they can be oriented in any fashion by the end customer). 
       FIG.  4    illustrates a system  30  that uses a B-type connectivity system using three Type B fiber optic jumper cables. Again, the following of the optical path  32  shows the required fiber optic jumper cables  12  along with the Type B adapter  34 , which mates fiber optic connectors key up to key up. See also  FIG.  6   . Again, if the polarity could be reversed become a significant advantages would result. Some of the prior art systems allow the removal of a key on one side and insertion on the other side, some use offset keys, and others require that at least a part outfit connect to be disassembled, and some have keys connected to the outer connector housing. All of these present significant disadvantages. Taking a fiber optic connector apart in the field has a risk of losing important parts. Not all systems use or need offset keys. And the removal of parts presents opportunities to damage the fiber optic connector, including the real danger of breaking off parts. Broken parts may not be able to be fixed and a completely new connector may have to be installed, With an increased installation time and costs. The present invention only requires a simple back-and-forth motion of a tool to achieve the desired results with little or no risk of damage or lost parts. 
     Referring to  FIG.  7   , a fiber optic connector  100  according to one embodiment of the present invention is illustrated. The fiber optic connector  100  includes a connector inner housing  102   a  and outer housing  102   b , and a fiber optic ferrule  104 . It may also include a spring  106 , a spring push  108 , a guide pin clamp (not shown), and guide pins  112  in guide pin holes  114 . As is known in the art, the fiber optic ferrule  104  is inserted into the inner connector housing  102   a  and it engages a seating surface  116 , which prevents the fiber optic ferrule  104  from traveling too far toward the front of the connector housing  102 . The spring  106  is inserted behind the guide pin clamp, which is behind the fiber optic ferrule  104  to bias the fiber optic ferrule  104  toward the seating surface  116 . A spring push  108  engages the back end of the spring  106  and the connector housing  102 , securing the fiber optic ferrule  104 , a spring  106 , the spring push  108 , and the guide pin clamp in the connector housing  102 . When the fiber optic connector  100  engages another fiber optic ferrule (not shown), the fiber optic ferrules  104  of the two fiber optic connectors engage one another, causing the spring  106  to be compressed between the guide pin clamp (which engages the rear end of fiber optic ferrule  104 ) and the spring push  108 . The fiber optic ferrule  104  is pushed rearwardly and the fiber optic ferrule  104  is unseated from the seating surface  116 . As long as the spring  106  squarely engages the back end  118  of the guide pin clamp, then the fiber optic ferrule  104  can appropriately engage the other fiber optic ferrule. 
     The fiber optic connector  100  also includes keys  120 , one on the top of the fiber optic connector  100  and one (see  FIG.  10   ) on the bottom of the fiber optic connector  100 . The keys  120  are the same (except that the keys have different colors in one embodiment to allow the orientation of the fiber optic connector to be more easily identified) for the top and the bottom of the fiber optic connector  100 . 
     The key  120  has a front end  122  and a rear end  124 . The front end  122  has a front wall  126  that protects the first latch  128 . The front wall  126  also prevents a fiber optic connector from being inserted into an adapter in the wrong orientation. The front end  122  also has a greater height than the rear end  124 . Extending through the length of the key  120  is an opening  130  to accommodate surfaces disposed in the recessed portions of the inner connector housing illustrated in  FIG.  9   . Each of the sides  132  has at the bottom a flared portion  134  that cooperates with the recessed portions of the inner connector housing  102   a  to create a sliding dovetail. See, e.g.,  FIG.  7   . Alternatively, other configurations for connecting the key  120  to the inner connector housing  102   a  could be used. 
     On each of the sides  132  of the key  120  are two notches  136  spaced just behind the front wall  124 . The notches  136  cooperate with a tool (see  FIGS.  11 - 13   ) to allow the key  120  to be pulled from a second position to a first position, as explained more detail below. While the notches  136  are v-shaped, they could be of any appropriate shape that cooperates with the tool and allows sufficient grasping forced to pull the key  120 . 
     In the front end  122  is a tab  140  and in the rear end  124  is a tab  142 , the tabs  140 ,  142  are connected to the key  120  along one side  144 ,  146 . This arrangement allows the tabs  140 ,  142  to flex both upward and downward, i.e., into the opening  130  and upwards away from the opening  130  for reasons that will be identified below. Attached at the free end of each of the tabs  140 ,  142  are latches  128 ,  148 , respectively. The latch  128  is a first latch that retains the key  120  in the first position and the second latch  148  retains the key  120  in the fiber optic connector  100  by preventing the key  120  from being removed. As will be made clear below, once the key  120  is disposed within the fiber optic connector  100 , it cannot be removed without completely removing the outer housing  102   b . Since the outer housing  102   b  is not intended to be removed once it is installed (and without damaging the fiber optic connector), the keys  120  are permanently installed in the fiber optic connector  100 . 
     One version of an inner connector housing  102   a  according to an embodiment of the present invention is illustrated in  FIG.  9   . The inner connector housing is typical for an MTP connector except for two features. The first are the recessed portions  160  (one on the top and one on the bottom, both being the same) to receive the key  120 . The second feature, which is not related to the present application but is different from a standard MTP inner connector housing are the openings  162 , which allow for access to a pin keeper that allows the gender of the fiber optic ferrule to be changed. Co-pending application Ser. No. 15/247,839, the contents of which are incorporated herein by reference, describes one such pin keeper and is assigned to the same applicant as the present application. A second application of this applicant, U.S. patent application Ser. No. 15/383,356, filed on Dec. 19, 2016, also discloses a second such pin keeper. The contents of the second application are also incorporated herein by reference. 
     The recessed portions  160  extend from a front end  164  of the inner connecting housing  102   a , without a front barrier to the recessed portions  160 . Such a configuration allows for the key  120  to be slid into the recessed portion from in front of the inner connector housing  102   a . The recessed portion has a central portion  166  and then an outer flared portion  168  that corresponds to the flared portion  134 . The recessed portion runs a substantial portion of the length of the inner connector housing  102   a —not quite twice the length of the key  120 . See, e.g.,  FIG.  11   . At the distal end  170  of the recessed portion  160  is a rear wall  172  to provide a stop for the key  120 . 
     Applicant notes that the term “front” or “forward” means that direction where the fiber optic connector would meet with another fiber-optic connector or device, while the term “rear” or “rearward” is used to mean the direction from which the optical fibers enter into the fiber-optic ferrule or fiber optic connector. Thus, “front” is that part of the inner connector housing  102   a  closest to the legend “ FIG.  9   ” and “forward” is out and downward from the page. See also  FIG.  7   . “Rear” is that part of the inner connector housing  102   a  that is on the top of the page and “rearward” is up and into the page. 
     Disposed within the recessed portion  160  is a raised center member  180 . The raised center member  180  has a forward facing surface  182  and a rearward facing surface  184 . The raised center member  180  is configured to pass through the opening  130  in the key  120 . The raised center member  180  and its particular location within the recessed portion  160  is also instrumental in the positioning of the key  120  in the first and second positions. There is also an indentation  186  in the raised center member  180  to receive the first latch  128 . The raised center member  180  could also be comprised of multiple smaller sections if so desired. The raised center member  180  provides the forward facing and rearward facing services, which could be done in alternative ways and still fall within the scope of the present invention. 
     Turning to  FIG.  10   , a cross sectional view along a longitudinal axis of the inner connector housing  102   a  and two keys  120  are illustrated. The other components of fiber optic connector  100  have been removed from the remaining figures for clarity purposes only. On the top of the inner connector housing  102   a  is a first key  120   t  while a second key  120   b  is disposed on the bottom of connector housing  102   a . Key  120   t  is in a first position—or the position that will determine the orientation of the fiber optic connector  100 . The second key  120   b  is in the second position, or a retracted position that does not affect the orientation of the fiber optic connector  100 . 
     The key  120   t  is slid into the recessed portion  160  so that the flared portion  134  engages the corresponding outer flared portion  168  to keep the key  120   t  within the fiber optic connector  100 . The second latch  148 , by virtue of latching surface facing forward and also having a chamfered leading edge (as the key  120   t  is pushed onto the inner connector housing  102   a ) and because it is on the flexible tab  142 , slides over the raised center portion  180  and past the rearward facing surface  184 . The second latch  148  would be hidden from view (and access) by the outer connector housing  102   b . See  FIG.  7   . At this point, the key  120   t  is prevented from traveling any farther rearwardly as the front latch  128  engages the forward facing surface  182 . With the front latch  128  protected by the front wall  126 , it is very difficult, if not impossible, for the front latch  128  to be moved unintentionally and without an appropriate tool to do so. Thus, insertion of a fiber optic connector into an adapter or other device with an incorrect orientation would be impossible with the key  120   t  in place as illustrated in  FIG.  10   . The key  120   t  also cannot be pulled out of the inner connector housing  102   a  because the second latch  148  engages the rearward facing surface  184 . 
     In viewing  FIG.  10   , the inner housing could be rotated 180 degrees so that the top is the bottom and the bottom is the top, but for the purposes of the discussion herein, the features remain the same regardless of the orientation. 
     Key  120   b  is in the second position on the bottom of the inner connector housing  102   a . Key  120   b  would preferably be placed in the second position before the fiber optic connector is assembled. However, it is possible, as discussed below with regard to the changing of polarity, to add both keys after the inner and outer connector housings are in place. 
     Key  120   b  has the first latch  128  in the indentation  186  in the raised center member  180  and the rear end  124  engaging the rear wall  172  at distal end  170 . With the first latch  128  in the indentation  186 , the key  120   b  will not be able to move within the fiber optic connector  100 , without using a tool to move it. 
     The tool  200  that is used to move one of the keys  120  rearward and one forward in a single action is illustrated in  FIGS.  11 - 13   . The tool  200  has a first side  202  that is aligned with the key  120  disposed in the first position. Thus, the second side  204  of tool  200  is aligned with the side of the fiber optic connector  100  with the key  120  in the second position. If the tool  200  is aligned incorrectly (second side  204  aligned with the key  120  in the first position), the tool  200  will not be able to move the key  120  as the latch  128  will prevent the key  120  from moving, thereby signaling to the user that the tool  200  needs to be reoriented with respect to the fiber optic connector  100 . 
     The first side  202  of the tool  200  has a leading prong  206  with a chamfered edge  208  at a first end  210 . On either side of the leading prong are two side extensions  212 , preferably with flat leading edges  214 , that engage the front wall  126  of the key  120 . Referring to  FIGS.  14  and  15   , the tool  200  is inserted around the inner connecting housing  102   a  and the chamfered edge  208  of the leading prong  206  engages the first latch  128 . See  FIG.  15   . This causes the first latch  128  to be lifted up and clear the forward facing surface  182 . Then as the tool  200  is inserted farther, the two side extensions  212  engage the front wall  126  and the key  120   t  is pushed rearwardly toward the rear wall  172 . Once the rear end  124  engages the rear wall  172 , the tool  200  can not be pushed any farther into the fiber optic connector  100 . This position is illustrated in  FIG.  16   . In the top left detail of  FIG.  16   , the first latch  128  is disposed in the indentation  186 , while in the top right detail of  FIG.  16    the rear end  124  is disposed against the rear wall  172 . At this point, it should be noted that both keys  120   t  and  120   b  are in the second position. However, the tool  200  is disposed as far into the fiber optic connector  100  as possible. The top key  120   t  will remain in this second position when the tool  200  is extracted. Nothing on the tool  200  engages the top key  120   t  such that pulling the tool  200  out will cause the top key  120   t  to come with it. Moreover, the first latch  128  is disposed within the indentation  186  which supplies resistance to removal of the top key  120   t.    
     Returning to the installation of the keys  120  after the inner and outer connector housings  102   a , 102   b  have been installed, one key  120   b  (again, the bottom reference merely indicates that the key will in this explanation will be in the second position), will be inserted into the recessed portion  160  as noted above. It can be pushed back into the inner connector housing  102   a , with or without the aid of the tool  200 , until the first latch  128  engages the forward facing surface  182 . The tool  200  then will be used as noted above to push the key  120   b  deeper into the recessed portion  160 —until it engages the rear wall  172 . Without a key  120  on the other side of the fiber optic connector  100 , the tool  200  will simply slide out, leaving the key  120   b  in the second position. A second key  120   t  (again because it will be in the first position) would be inserted into the opposite side of the fiber optic connector  100  with or without the use of the tool  200  until the first latch  128  engages the forward facing surface  182 . Now there are two keys  120  installed in the fiber optic connector  100 . Alternatively, the keys  120  may also be installed from the back side of the inner connector housing  102   a  before outer connector housing  102   b  is installed. 
     Returning to  FIGS.  11 - 13   , these figures are used to describe the second side  204  of the tool and moving the key  120   b  from the second position to the first position. The second side  204  of the tool  200  has two tabs  216  at the first end  210 . Each of the tabs  216  has a protrusion  218  on an inside portion of the tabs  216  and therefore the protrusions  218  face each other. The protrusions  218  have a v-shape that correspond to the notches  136  on the front end  122  of the keys  120 . It is the engagement of the protrusions  218  with the notches  136  that allows the tool  200  to move the key  120   b  from the second position to the first position. This will be explained with reference to  FIGS.  17  and  18   . In  FIG.  17   , the tool  200  is inserted as far as possible after moving key  120   t  from the first position to the second position. At this location, the tabs  216  have passed by the front end  122  of the key  120   b  and the protrusions  218  have engaged the notches  136 . See  FIG.  18   , which shows one side of the tool  200  engaging the key  120   b  and, in particular, the tab  216  and protrusion  218  in the notch  136 . The force of the tool  200  on the front end  122  of the key  120   b  in the notches  136  is greater than the force required to move the first latch  128  out of the indentation  186  in the recessed portion  160 . As the tool  200  is pulled out of the fiber optic connector  100 , the key  120   b  is moved with the tool  200 . See  FIG.  19   . The second latch  148  will then engage the rearward facing surface  184 , preventing any further forward movement of the key  120   b . As the tool is continued to be pulled, the tabs  216  will flex open allowing the key  120   b  to be freed from the tool  200 . At this point, the first latch  128  will be in front of the forward facing surface  182  and the key  120   b  is now in the first position. As noted above, the key  120   t  is left in the second position and the two keys  120  have been reversed in position within the fiber optic connector  100 . See  FIG.  20   . 
     In the key  120  illustrated in  FIG.  8    and as noted above, the front latch  128  engages the forward facing surface  182  of the inner connector housing  102   a  and prevents the key  120  from moving relative to the inner connector housing  102   a  and also prevents the fiber optic connector  100  from being inserted in an incorrect orientation. As illustrated in  FIG.  21   , a rearward applied force RAF (when inserted incorrectly) on the front wall  126  of the key  120  requires that the forward facing surface  182  apply a reaction force RF to be equal and opposite to that rearward applied force RAF. These forces are more fully illustrated in  FIG.  22   . Based upon the design of the key  120  the location of the rearward applied force RAF on the key  120  and the reaction force RF, there is a tensile load and a bending load in front latch  128 . 
       FIG.  23    illustrates the effect of the tensile load and bending load on the latch  120 . The tab  140  that carries the front latch  128  will start to lift relative to the inner connector housing  102   a  as the loads increase. As illustrated, the front latch  128  will rotate in a counterclockwise direction, changing the latch angle by an angle α. There may also be deformation of the forward facing surface  182  of the inner connector housing  102   a . As the forces increase, the key  120  will eventually fail for one of two reasons, allowing the key  120  to be pushed in a rearward direction and not provide the keying function. The first of these two failures is when the latch angle exceeds α=tan −1 (1/μ) (where μ is the coefficient of friction) allowing the front latch  128  to release from the forward facing surface  182  of the inner connector housing  102   a.    
     The second of these failures comes when the stress (or compression or deformation) exceeds the material strength, resulting in the breaking of the latch (and or the surface  182 ), again allowing the key  120  to move in a rearward direction. 
     Another embodiment of a key  300  according to the present invention is illustrated in  FIGS.  24 - 26   . The key  300  has a main body  302  that extends from a front end  304  to a rear end  306 . At the front end  304  has a cantilevered portion  308  that extends from a central portion  310  of the main body  302  towards the front end  304 . The cantilevered portion  308  may diverge into two arms  312 ,  314 , although it may be a singularity. 
     The key  300  also has first portion  316  and second portion  318  that extend from the central portion  310  of the main body  302  along opposite sides of the cantilevered portion  308 . The first and second side portions  316 , 318  each have a flared portion  320  along opposing edges  322 , 324  to engage the inner connector housing  102   a  and to create a sliding dovetail. See  FIG.  9    and corresponding text. Extending along the length of the underside of the main body  302  is an opening  330  to accommodate surfaces and features disposed in the recessed portions of the inner connector housing, such as those illustrated in  FIG.  9   . The main body  302  has a rear surface  332  that faces to the front end  304  of the key  300  that may provide a stop surface and prevent the key  300  from being pulled from the fiber optic connector  100 . There may be surfaces, such as the rearward facing surface  184 , in the inner connector housing  102   a  that are used to limit the movement of the key  300 . On the opposite side of rear surface  332  is another rearward facing surface  334  that may engage a rear wall  172  of the inner connector housing  102   a  to prevent the key  300  from being pushed too far into the inner connector housing  102   a.    
     In the central area  340  between the two arms  312 ,  314  of the cantilevered portion  308  and extending into the opening  330  is a latch  342 . See  FIG.  25   . The latch  342  corresponds to and performs similar functions as the latch  120 . Turning to  FIGS.  27 - 29   , the latch  342  engages a forward facing surface  182  to prevent the key from being pushed rearwardly. It should be noted that the forward facing surface  182  and the latch  342  may not be perpendicular to the longitudinal axis A through the inner connector housing  102   a . In this case, the forward facing surface  182  and the latch  342  are disposed at an angle of β. See  FIG.  28   . The values for the angle of β may range from +10° to −10° off the vertical in  FIG.  28   . This assists in maintaining contact between the forward facing surface  182  and the latch  342 , thereby preventing slippage of those surfaces and the rotation of the latch  342  when under stress/compression. 
     The key  300  also has different heights or thicknesses at the different ends thereof. As with the prior embodiment, the front end  304  has a greater height than the rear end  306 . When oriented correctly, the key  300  will pass into the adapter  400  without issue. If oriented incorrectly, the larger front end  304  of the key, and the cantilevered portion  308  in particular, will hit the adapter  400  with the adapter engagement surface  350  at point A thereby preventing the fiber optic connector from being inserted into the adapter  400 . Prior to contact with point A, as the fiber optic connector  100  is entering the adapter  400 , the cantilevered portion  308  is in a relaxed first state. Subsequently, upon contact with point A, the cantilevered portion  308  encounters aforementioned forces that cause the cantilevered portion  308  to be in a compressed second state. In this compressed state, the cantilevered portion  308  is pushed against the forward facing surface  182 , and is prevented from moving further rearward, thereby preventing incorrect polarity insertion of the fiber optic connector  100  into the adapter  400 . 
     The adapter engagement surface  350  of the cantilevered portion  308  has a forward facing surface. As can be particularly seen in  FIGS.  24  and  26   , the adapter engagement surface  350  may have two different portions that are disposed at different angles relative to the longitudinal axis A. The bottom portion of the adapter engagement surface  350  is more vertical and then transitions into a more horizontal surface. The adapter engagement surface  350  is designed to engage the adapter  400  if the fiber optic connector is not correctly oriented. See  FIG.  29   . It is at this position that the adapter  400  will engage the key  300 . See  FIGS.  29  and  30   . When the adapter  400  makes contact with the adapter engagement surface  350  as illustrated, the forces and the moments in the latch  342  are balanced, and the latch is more secure than that of the prior embodiment. 
     On the outsides of each of the arms  312 ,  314  of the cantilevered portion  308  are two notches  360  spaced just behind the front end  304 . The notches  360  cooperate with the tool (see  FIGS.  11 - 13   ), or a similar tool, to allow the key  300  to be pulled from the second position to the first position as explained above. The notches  360  are v-shaped, but they could be of any appropriate shape that cooperates with the tool and allows sufficient grasping forced to pull the key  300 . 
     Another embodiment of a key  500  according to the present invention is illustrated in  FIGS.  31 - 33   . The key  500  has a main body  502  that extends from a front end  504  to a rear end  506 . At the front end  504  has a cantilevered portion  508  that extends from a central portion  510  of the main body  502  towards the front end  504 . At the front end of the cantilevered portion  508  are two flared or knuckle portions  512 , 514  that extend outward from the cantilevered portion  508 . 
     The key  500  also has first portion  516  and second portion  518  that extend from the central portion  510  of the main body  502  along opposite sides of the cantilevered portion  508  and end at a front wall  520 . The first and second side portions  516 , 518  each have a flared portion  522  along opposing edges  524 , 526  to engage the inner connector housing  102   a  and to create a sliding dovetail. See  FIG.  9    and corresponding text. Extending along the length of the underside of the main body  502  is an opening  530  to accommodate surfaces and features disposed in the recessed portions of the inner connector housing  102   a , such as those illustrated in  FIG.  29   . The main body  502  has a rear surface  532  that faces to the front end  504  of the key  500  to provide a stop surface and prevent the key  500  from being pulled from the fiber optic connector  100 . There may be surfaces, such as the rearward facing surface  184 , in the inner connector housing  102   a  that are used to limit the movement of the key  500 . On the opposite side of rear surface  532  is another rearward facing surface  534  that may engage a rear wall  172  to prevent the key  500  from being pushed too far into the inner connector housing. 
     In the central area  540  of the cantilevered portion  508  and extending into the opening  530  is a latch  542 . The latch  542  corresponds to and performs similar functions as the latches  342  and  120 . 
     In this embodiment, if the key  500  engages the adapter, the front wall  520  is the structure on the key  500  that will engage the adapter. As is clear from  FIG.  32   , a central part  560  of the front wall  520  will move over the front of the cantilevered portion  508 , thereby preventing the latch to move upward and away from the forward facing surface  182 . The side portions of the front wall  520  will also move rearwardly to engage the two flared or knuckle portions  512 , 514 , also preventing the cantilevered portion  508  and the latch  542  from moving upward and away from the forward facing surface  182 . 
     Another embodiment of a key  600  according to the present invention is illustrated in  FIGS.  34 - 36   . The key  600  has a main body  602  that extends from a front end  604  to a rear end  606 . Towards the front end  604  is a cantilevered portion  608  that extends from a central portion  610  of the main body  602  towards the front end  604 . 
     The key  600  also has first portion  616  and second portion  618  that extend from the central portion  610  of the main body  602  along opposite sides of the cantilevered portion  608  and end at a front wall  620 . The first and second side portions  616 , 618  each have a flared portion  622  along opposing edges  624 , 626  to engage the inner connector housing  102   a  and to create a sliding dovetail. Extending along the length of the underside of the main body  602  is an opening  630  to accommodate surfaces and features disposed in the recessed portions of the inner connector housing, such as those illustrated in  FIG.  29   . The main body  602  has a rear surface (not shown) that faces to the front end  604  of the key  600  to provide a stop surface and prevent the key  600  from being pulled from the fiber optic connector. There may be surfaces, such as the rearward facing surface  184 , in the inner connector housing  102   a  that are used to limit the movement of the key  600 . On the opposite side of rear surface is another rearward facing surface  634  that may engage a rear wall  172  to prevent the key  600  from being pushed too far into the inner connector housing. 
     In the central area  640  of the cantilevered portion  608  and extending into the opening  630  is a latch  642 . The latch  642  corresponds to and performs similar functions as the latches  342  and  120 . 
     In this embodiment, if the key  600  engages the adapter, the front wall  620  is the structure on the key  600  that will engage the adapter. The central part  660  of the front wall  620  will move slightly in a rearward direction and over the front of the cantilevered portion  608  (and latch  642 ), thereby preventing the latch to move upward and away from the forward facing surface on the inner connector housing (not shown for clarity). 
     Another embodiment of a key  700  according to the present invention is illustrated in  FIGS.  37 - 39   . The key  700  has a main body  702  that extends from a front end  704  to a rear end  706 . Towards the front end  704  is a cantilevered portion  708  that extends from a central portion  710  of the main body  702  towards the front end  704 . 
     The key  700  also has first portion  716  and second portion  718  that extend from the central portion  710  of the main body  702  along opposite sides of the cantilevered portion  708 . The first and second side portions  716 , 718  each have a flared portion  722  along opposing edges  724 , 726  to engage the inner connector housing  102   a  and to create a sliding dovetail. 
     The first and second side portions  716 , 718  stop near the front of the cantilevered portion  708 , but the lower portions on each side, where the flared portion  722  is, continue past the cantilevered portion  708  and end at a front wall  720 . This causes there to be space  728  between the wall and the first and second side portions  716 , 718  and cantilevered portion  708 . Thus, the front wall  720  is connected to the key  700  by a reduced amount of material. 
     Extending along the length of the underside of the main body  702  is an opening  730  to accommodate surfaces and features disposed in the recessed portions of the inner connector housing  102   a , such as those illustrated in  FIG.  29   . The main body  702  has a rear surface (not shown) that faces to the front end  704  of the key  700  to provide a stop surface and prevent the key  700  from being pulled from the fiber optic connector  100 . There may be surfaces, such as the rearward facing surface  184 , in the inner connector housing  102   a  that are used to limit the movement of the key  700 . On the opposite side of rear surface is another rearward facing surface  734  that may engage a rear wall  172  to prevent the key  700  from being pushed too far into the inner connector housing  102   a.    
     In the central area  740  of the cantilevered portion  708  and extending into the opening  730  is a latch  742 . The latch  742  corresponds to and performs similar functions as the other latches. See  FIG.  38   . 
     In this embodiment, if the key  700  engages the adapter, the front wall  720  is the structure on the key  700  that will engage the adapter. The front wall  720 , connected to the rest of the key  700  with the reduced material, is flexible and will rotate rearward into the space  728  with the force from the adapter. The front wall  720  will engage the cantilevered portion  708  as illustrated in  FIG.  39   . This will keep the latch  742  from disengaging and allowing the key to move rearward. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and variations of this invention provided they come within the scope of the appended claims and their equivalents.