Patent Publication Number: US-11650376-B2

Title: Optical fiber connectors

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/962,242, filed Jan. 17, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to optical fiber connectors, for example SC-style connectors, and to a method of forming and using such connectors. 
     The mechanical tolerances involved in terminating single mode optical fiber are much tighter than those for multimode optical fiber. Therefore, while it is quite common for multimode optical fiber be terminated at the point of use, for example, at a user&#39;s premises or at an outside junction box, in most product applications, single mode optical fiber is not terminated in the field. When single mode fiber must be terminated in the field, then it can take a skilled technician between about 15 to 20 minutes to splice fibers together either by using a V-groove clamp or expensive fusion welding equipment. 
     Single mode fiber is therefore often provided in a range of different lengths, pre-terminated at both ends with a connector plug ready to plug into a matching receptacle. Commonly, eight or twelve single mode optical fibers may be bundled together in an optical fiber cable having an outer protective tube inside of which the optical fibers run. 
     An example of such a connector is the “Subscriber Connector,” or SC connector, originally developed by NTT®. SC connectors have convenient push/pull style mating, and are approximately square in cross-section and with a 2.5 mm diameter ferule at the termination of the optical fiber, surrounded by a plastic housing for protection. SC connectors are available in single or duplex configurations. The SC connector latches into a matching socket in a simple push motion. The push-pull design includes a spring against which the ferrule slides within a plastic inner housing. This arrangement provides a reliable contact pressure at the ferrule end and resists fiber end face contact damage of the optical fiber during connection. The connector can be quickly disconnected by first pulling back an outer housing, which is slidable relative to the inner housing, to disengage a latch inside socket between the socket and the inner housing, before pulling the optical fiber connector from the socket. Until the latch is thus disengaged, the latch prevents withdrawal of the connector when the optical fiber cable is pulled in a direction away from the socket. 
     It is important to avoid bending optical fiber around curves having too sharp a bend radius, as this will increase optical losses and can permanently damage the optical fiber. Optical fiber cables are therefore often routed inside a protective outer tube or conduit, which can have minimum bend-limiting properties. Protective bend limiting conduits normally have an outer diameter of 8 mm or 10 mm tubes. The cross-section of a standard SC connector has dimensions of about 7 mm×9 mm, and even a small form factor SC connector is too large to fit inside the inner diameter of a typical protective conduit. 
     Conventional optical fiber connectors comprise a rigid pushable structure to allow for limited movement of the connector parts while being pushed down stretches of duct. However, due to their rigid structure, conventional optical fiber connectors suffer from signal degradation when weight is added to the cable and the connector while the connector is transmitting a signal. 
     It may be desirable to provide an optical fiber connector with improved signal transmission capability. 
     SUMMARY 
     In accordance with various aspects of the disclosure, an optical fiber connector sub-assembly for an optical fiber connector including a ferrule configured to hold an optical fiber therein along an axis of the connector, a ferrule holder configured to hold the ferrule at a front portion of the connector, a ferrule housing including a front portion configured to slidingly receive the ferrule holder and a rear portion terminating a fiber optic cable that includes the optical fiber, and an inner housing configured to fixed coupled with the ferrule housing. The ferrule is configured to terminate the optical fiber. The ferrule holder, the ferrule housing, and the inner housing are configured to be rotatably fixed to one another. The ferrule holder is configured to slide axially relative to the inner housing. 
     In some aspects, the front portion includes a cylindrical portion and two arms extending from a forward end of the cylindrical portion, and the ferrule holder includes a base portion having two notches configured to receive the two arms. 
     According to various aspects, an outer surface of the front portion includes axially extending notches configured to receive projections extending radially inward from an inner wall of the inner housing. 
     According to some aspects, the ferrule holder and the ferrule housing are configured to move axially relative to one another along the connector axis between limits defined by an interaction between the ferrule housing and the ferrule holder. In various aspects, a spring is provided between the ferrule holder and the ferrule housing and configured to bias the ferrule away from the ferrule housing along the connector axis. 
     In various aspects, outermost surfaces of the ferrule housing and the ferrule holder, relative to the connector axis, lie on a common cylindrical envelope. 
     According to various aspects, a Subscriber Connection (SC)-type optical fiber connector includes one of the aforementioned optical fiber connector sub-assemblies and an outer housing. The inner housing defines a receptacle for a socket to receive a projecting portion of the ferrule. The spring provided between the ferrule holder and the ferrule housing is configured such that the projecting portion of the ferrule is spring biased along the connector axis towards the receptacle of the inner housing. The inner housing is configured to be engaged within the outer housing, the inner housing and the outer housing being configured to move relative to each other along the connector axis between limits defined by an interaction between the inner housing and the outer housing in order to provide SC-style push/pull engagement/disengagement with a mating optical fiber socket. 
     In some aspects, of the SC-type optical fiber connector, the ferrule is configured to be rotationally fixed with respect to the ferrule holder about the connector axis, and the ferrule holder is configured to be rotationally aligned with respect to the outer housing so that the rotational orientation of the ferrule with respect to the outer housing can be set during assembly of the connector at one of one or more predefined rotational orientations. 
     In various aspects of the SC-type optical fiber, a first rotational key is provided between the ferrule holder and the ferrule housing and a second rotational key is provided between the ferrule housing and the inner housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which: 
         FIG.  1    is an exploded perspective view of an exemplary prior art SC connector; 
         FIG.  2    is a perspective view of the optical fiber connector sub-assembly of  FIG.  1    when assembled; 
         FIG.  3    is a perspective view of an exemplary optical fiber connector sub-assembly in accordance with various aspects of the disclosure terminating an optical fiber cable; 
         FIG.  4    is a perspective cross-sectional view of the optical fiber connector sub-assembly of  FIG.  3   ; 
         FIG.  5    is a perspective view of an exemplary SC connector including the optical fiber connector sub-assembly of  FIG.  3   ; 
         FIG.  6    is a top cross-sectional view of the ferrule housing of the optical fiber connector sub-assembly of  FIG.  3   ; 
         FIG.  7    is a perspective cross-sectional view of the ferrule housing of  FIG.  6   ; 
         FIG.  8    is a perspective view of an exemplary optical fiber connector sub-assembly in accordance with various aspects of the disclosure terminating an optical fiber cable; 
         FIG.  9    is a perspective view of the optical fiber connector sub-assembly of  FIG.  8    when assembled; 
         FIG.  10    is a perspective view of an exemplary SC connector including the optical fiber connector sub-assembly of  FIG.  8   ; 
         FIG.  11    is a perspective cross-sectional view of the exemplary SC connector of  FIG.  10   ; and 
         FIG.  12    is a side cross-sectional view of the exemplary SC connector of  FIG.  10   . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIGS.  1  and  2    show an exemplary prior art SC connector, such as the connectors disclosed in U.S. patent application Ser. No. 15/887,925, the disclosure of which is incorporated herein by reference. The exemplary SC connector  100  includes an optical fiber cable  102 , a ferrule housing sub-assembly  104 , and an outer housing  140  to provide SC-style push/pull engagement/disengagement with a mating optical fiber socket (not shown). 
     The cable  102  holds an optical fiber  108 , for example, a single strand of 125 μm diameter single mode optical fiber, protected by primary and secondary buffering layers  110 , about 900 μm in diameter, and an outer sheath  112 , typically 3 mm to 5 mm in diameter. The optical fiber  108  is terminated by a ferrule  114  in a manner well-known to those skilled in the art, and defines a ferrule axis  105  that extends centrally through the SC connector  100 . 
     The ferrule housing sub-assembly  104  includes the cylindrical ceramic ferrule  114 , a ferrule basket  116  in which the ferrule is seated, a helical spring  117 , a ferrule housing  155 , and an inner housing  120 . The ferrule housing  155  includes a cylindrical sleeve portion  136  and a ferrule basket carrier portion  150 . The ferrule basket carrier portion  150  may include longitudinal slots  180  along the lengths of their outer surfaces that are keyed to projections (not shown) on an inner surface of the inner housing  120  to prevent the ferrule housing  155  from rotating relative to the inner housing  120 . 
     The ferrule basket  116  has a base  115  and a cylindrical stem  122  which extends from the base  115  in an axial direction away from the ferrule  114  towards the cylindrical sleeve portion  136 , which is used to make a crimp connection around the optical fiber cable sheathing  112 . The spring  117  is seated around the stem  122  between an annular shoulder  124  on the ferrule basket  116  and an annular surface  152  within a cylindrical recess  154  of the ferrule basket carrier portion  150 . The stem  122  is slidably seated in a bore of the ferrule housing  155 . 
     During assembly, the ferrule basket  116  and seated ferrule  114  are inserted axially into the recess  154  of the ferrule basket carrier portion  150 . The ferrule basket carrier portion  150  has a pair of arms  156  that extend axially forwards of the stem  122  on opposite sides of the ferrule basket  116 . Two pairs of curved fingers  158  are provided, each pair extending in opposite circumferential directions at the end of each arm  156 . The fingers  158  extend transversely to the length of the arms  156  partially around the circumference of a portion of the ferrule  114  nearest a base  115 . 
     The ferrule base  115  has four cycles of crenellations  162  spaced symmetrically around the circumference of the base and which provide four corresponding channels that extend parallel to the optical fiber axis  105 . These crenellations  162  are in the form of alternating radially high  165  and low  166  cylindrically shaped regions with the circumferential and axial extent of each of the high  165  and low  166  regions being the same. The high  165  and low  166  regions are separated by steps  167  that extend in a radial direction. The arms  156  are seated in opposite radially low regions  166  in a sliding fit with the adjacent high regions  165 , and reach axially forward of the base  115  and crenellations  162  so that the fingers  158  engage with the intervening radially high regions  165  on a side  161  of the base  115  opposite the annular surface  124  against which the spring  117  is engaged. 
     The aforementioned arrangement permits a degree axial movement of the ferrule basket carrier portion  150 , with movement being therefore limited in one direction by the compression of the spring  117  between the two annular surfaces  124 ,  152  and in the other axial direction by the contact of the fingers  158  with the radially high regions  165  of the crenellations  162  on the base  115  of the ferrule basket  116 . As can be seen from the drawings, the ferrule holder base  115  and ferrule basket carrier portion  150  also have a common cylindrical outer envelope. 
     The inner housing  120  has a forward portion  130  that coaxially extends around the axially projecting ferrule  114  to define a receptacle  132  for a socket (not shown) to receive a projecting portion of the ferrule  114 . 
     The ferrule basket  116  is free to move backwards inside the ferrule basket carrier portion  150  and the inner housing  120  when an end face  134  of the ferrule  114  comes into contact with a similar end face (not shown) of another optical fiber ferrule when making an optical connection. 
     The ferrule basket carrier portion  150  has a central aperture (not shown) through which the optical fiber  108  and buffering  110  pass, and has in a rear-most portion the sleeve  136  configured to receive and be crimped to the cable sheathing  112 . In some aspects, a strain-relief sleeve (not shown), for example, a boot, may be provided around the junction of the optical fiber cable  102  and the ferrule housing sub-assembly  104 . 
     An outer housing  140  is press-fitted axially over the assembled ferrule housing sub-assembly  104 . Once the inner housing  120  and outer housing  140  are engaged together, the inner and outer housings are relatively moveable with respect to each other along the ferrule axis  105  between limits defined by an interaction between the inner housing  120  and the outer housing  140  provided by projections  142  on a pair of opposite sides of the inner housing  120  and a pair of apertures  144  in the outer housing. The projections  142  and apertures  144  interact with sprung features inside a matching socket (not shown) to provide SC-style push/pull engagement/disengagement configured to mate with an optical fiber socket. 
     The rotational orientation of the ferrule basket carrier portion  150  may be set at one of four orientations relative to the ferrule  114  in the ferrule basket  116  owing to the seating of the arms  156  in the crenellations. In this way, a first rotational key is provided between the ferrule basket  116  and the ferrule basket carrier portion  150  such that the ferrule basket  116  and the ferrule basket carrier portion  150  are rotatably fixed to one another (i.e., are not rotatable relative to one another). 
     The optical fiber  108  is therefore terminated in a sub-assembly referred to herein as an optical fiber connector sub-assembly  160 , as illustrated in  FIG.  2   . During assembly of the optical fiber connector sub-assembly  160 , the arms  156  and the fingers  158 , which each have a chamfered taper  164  on an inner forwards surface, flex outwardly over the base  115  of the ferrule holder  114  until the fingers  158  snap radially inwards into engagement with the forwards surface  161  of the ferrule basket base  115 . 
     In both cases, the resulting optical fiber connector sub-assembly  160  is therefore mechanically whole or integral, both as regards the components forming the sub-assembly and as regards the mechanical connection of the sub-assembly to the optical fiber cable  102 . The sub-assembly cannot come apart without first prizing the fingers  158  back over the ferule basket base  115 . The ferrule basket carrier portion  150  has an outer diameter which is preferably no more than that of the widest portion of the ferrule basket  116 , i.e. the ferrule basket base  115 . 
     After the insertion has been performed, the assembly of the SC-type optical fiber connector  100  is completed as follows. The inner housing  120  is inserted in an axial direction over the projecting ferrule  114  and surrounding ferrule basket carrier portion  150 . The external shape of the inner housing  120  where this interacts with the outer housing  140  is the same as with conventional connectors. The outer housing  140  therefore is snap-fitted over the inner housing  120 , after which the SC-type connector  100  is fully compatible with conventional connectors and conventional optical fiber sockets. 
     Referring now to  FIGS.  3 - 7   , an exemplary optical fiber connector  200 , for example, an SC-type connector, in accordance with various aspects of the disclosure is illustrated and described. The connector  200  includes an optical fiber cable  102 , a ferrule housing sub-assembly  204 , and an outer housing (not shown) to provide SC-style push/pull engagement/disengagement with a mating optical fiber socket (not shown). 
     The ferrule housing sub-assembly  204  includes a cylindrical ceramic ferrule  214 , a ferrule basket  216  in which the ferrule  214  is seated, a helical spring  217 , a ferrule housing  255 , and an inner housing  220 . The ferrule housing  255  includes a front tube portion  250 , a rear tube portion  236 , and a connecting tube portion  237  between the front and rear tube portions  250 ,  236 . The connecting tube portion  237  has a smaller outside diameter than the adjacent front tube portion  250  and rear tube portion  236   
     The ferrule basket  216  has a base  215  and a cylindrical stem  222  which extends from the base  215  in an axial direction away from the ferrule  214  towards the rear tube portion  236 , which is used to make a crimp connection around the optical fiber cable sheathing  212 . The spring  217  is seated around the stem  222  between an annular shoulder  224  on the ferrule basket  216  and an annular surface  252  within a cylindrical recess  254  at a rearward end of the front tube portion  250 . The stem  222  slidably extends through an opening  239  at the rearward end of the front tube portion  250  and into the connecting tube portion  237 . A rearward end of the stem  222  includes a flared end portion  223 . The flared end portion  223  has a diameter greater than a diameter of the opening  239  such that forward axial movement of the stem  222  relative to the ferrule housing  255  is limited by interaction of the flared end portion  223  with a rearward-facing shoulder  241  in the connecting tube portion  237  at the opening  239 . 
     The ferrule basket  216  is configured to be inserted axially into the recess  254  of the front tube portion  250 . The front tube portion  250  has a pair of diametrically opposed arms  256  that extend axially forward of the stem  222  on opposite sides of the ferrule basket  216 . The ferrule base  215  has four cycles of crenellations  262  spaced symmetrically around the circumference of the base and which provide four corresponding channels that extend parallel to the optical fiber axis  205 . These crenellations  262  are in the form of alternating radially high  265  and low  266  cylindrically shaped regions with the circumferential and axial extent of each of the high  265  and low  266  regions being the same. The high  265  and low  266  regions are separated by steps  267  that extend in a radial direction. The arms  256  are seated in two opposite radially low regions  266  in a sliding fit with the adjacent high regions  265 . 
     The aforementioned arrangement permits a degree of axial movement of the ferrule basket  216  and ferrule  214  relative to the ferrule housing  255 , with movement being therefore limited in one direction by the compression of the spring  217  between the two annular surfaces  224 ,  252  and in the other axial direction by the contact of the flared end portion  223  of the stem  222  with the rearward-facing shoulder  241  in the connecting tube portion  237 . As can be seen from the drawings, the ferrule holder base  215  and front tube portion  250  also have a common cylindrical outer envelope. 
     The inner housing  220  has a forward portion  230  that coaxially extends around the axially projecting ferrule  214  to define a receptacle  232  for a socket (not shown) configured to receive a projecting portion of the ferrule  214 . The ferrule basket  216  is free to move backwards inside the front tube portion  250  and the inner housing  220  when an end face  234  of the ferrule  214  comes into contact with a similar end face (not shown) of another optical fiber ferrule when making an optical connection. 
     The front tube portion  250  of the ferrule housing  255  may include longitudinal notches  270  in its top and bottom outer surfaces that are keyed to axially-extending projections  272  ( FIGS.  6  and  7   ) on top and bottom inner surfaces of the inner housing  220  to prevent the ferrule housing  255  from rotating relative to the inner housing  220 . As shown in  FIG.  4   , the notches  270  are axially aligned with two of the low regions  266  of the crenellations  262  that are not occupied by the arms  256 . The depth of the notches  270  is less than a depth of the low regions  266  relative to outer profiles of the front tube portion  250  and the high regions  265  of the ferrule base  215 , which are substantially the same as one another. 
     Referring now to  FIGS.  6  and  7    (illustrating only the bottom projection  272 ), a rearward end of the receptacle  232  is bounded by a wall portion  233  having an opening  235  with a dimension that is smaller than a cross-sectional dimension of the receptacle. The projections  272  extend rearward from the wall portion  233  and radially inward from the wall portion  233  of the inner housing  220 . The projections  272  include a first portion  276  having a width in a direction transverse to the axial direction that tapers from an inner wall  229  to a second portion  278 . The second portion  278  of the projection  272  has a substantially constant width dimension. The first portion  276  and the second portion  278  have a substantially contact radial thickness. The projections  272  include a third portion  280  extending from the second portion  278 . The third portion  280  includes a substantially same width dimension as the second portion  278 , but the third portion  280  includes a radially thickness that tapers from the second portion  278  to a smaller substantially constant thickness along a majority of a length of the third portion  280 . At a rearward end of the third portion  280 , the thickness tapers to the inner wall  229  of the inner housing  220 . Although only the bottom projection  272  is illustrated, it should be understood that the top wall of the inner housing  220  includes an identical projection. 
     As a result of the aforementioned structures of the projections  272 , the notches  270 , and the low regions  266 , the inner housing  220  and the ferrule housing  255  are rotatably coupled to one another. As the inner housing  220  is slipped over the ferrule housing  255 , the low regions  266  and notches  270  are aligned with the projections  272 . A width dimension of the low regions  266  and notches  270  is greater than the width of the second and third portions  278 ,  280  of the projections  272  to facilitate insertion of the ferrule housing  255  into the inner housing  220 . The low regions  266  have a width dimension sized to engage the first tapered portion  276  of the projections  272  so as to be spaced from a rear surface of the wall portion  233  of the receptacle  232 . A total length of the first and second portions  276 ,  278  of the projections  272  is sized to extend through the low regions  266  in the axial direction without entering the notches  270 , thus allowing the ferrule basket  216  to slide along the second portion  278  when the ferrule basket  216  slides axially relative to the ferrule housing  255 . The third portion  280  has a length that extends into the notches  270 , while allowing the inner housing  220  and the ferrule basket  216  to slide axially relative to the ferrule housing  255  without such axial sliding movement being limited by the thicker second portion  278 . 
     The front tube portion  250  has a central aperture (not shown) through which the optical fiber  108  and buffering  110  pass, and has in a rear-most portion the sleeve  236  configured to receive and be crimped to the cable sheathing  112 . In some aspects, a strain-relief sleeve (not shown), for example, a boot, may be provided around the junction of the optical fiber cable  102  and the ferrule housing sub-assembly  204 . 
     An outer housing is press-fitted axially over the assembled ferrule housing sub-assembly  204 . Once the inner housing  220  and outer housing are engaged together, the inner and outer housings are relatively moveable with respect to each other along the ferrule axis  205  between limits defined by an interaction between the inner housing  220  and the outer housing provided by projections  242  on a pair of opposite sides of the inner housing  220  and a pair of apertures (not shown) in the outer housing. The projections  242  and apertures interact with spring features inside a matching socket (not shown) to provide SC-style push/pull engagement/disengagement configured to mate with an optical fiber socket. 
     The rotational orientation of the front tube portion  250  may be set at one of four orientations relative to the ferrule  214  in the ferrule basket  214  owing to the seating of the arms  256  in the crenellations  262 . In this way, a first rotational key is provided between the ferrule basket  216  and the front tube portion  250  such that the ferrule basket  216  and the front tube portion  250  are rotatably fixed to one another (i.e., are not rotatable relative to one another). 
     The optical fiber  108  is therefore terminated in a sub-assembly referred to herein as an optical fiber connector sub-assembly  260 . The resulting optical fiber connector sub-assembly  260  is therefore mechanically whole or integral, both as regards the components forming the sub-assembly and as regards the mechanical connection of the sub-assembly to the optical fiber cable  102 . The front tube portion  250  has an outer diameter which is preferably no more than that of the widest portion of the ferrule basket  216 , i.e. the crenellations  262  of the ferrule basket base  215 . 
     After the insertion has been performed, the assembly of the SC-type optical fiber connector  200  is completed as follows. The inner housing  220  is slid in an axial direction over the projecting ferrule  214  and surrounding front tube portion  250 . The inner housing  220  includes latches  221  on opposite side walls  223 . For example, the latches  221  may be disposed in cutouts  225  in the side walls  223  of the inner housing. The latches  221  may extend forwardly from a rearward wall  227  of the cutouts  225 . When the inner housing  220  is slid over the front tube portion  250 , the latches  221  are configured to deflect outwardly and when the connecting tube portion  237  of the ferrule housing  255  reaches the latches  221 , the latches  221  move inwardly toward the connecting tube portion  237  to a position in the annular groove  238  between the front tube portion  250  and the rear tube portion  236 , thereby fixing the position of the ferrule housing  255  relative to the inner housing  220 . The external shape of the inner housing  220  where this interacts with the outer housing  240  is the same as or similar to conventional connectors. The outer housing therefore is snap-fitted over the inner housing  220 , after which the SC-type connector  200  is fully compatible with conventional connectors and conventional optical fiber sockets. 
     Referring now to  FIGS.  8 - 12   , an exemplary optical fiber connector  300 , for example, an SC-type connector, in accordance with various aspects of the disclosure is illustrated and described. The connector  300  includes an optical fiber cable  102 , a ferrule housing sub-assembly  304 , and an outer housing  340  to provide SC-style push/pull engagement/disengagement with a mating optical fiber socket (not shown). 
     The ferrule housing sub-assembly  304  includes a cylindrical ceramic ferrule  314 , a ferrule basket  316  in which the ferrule  314  is seated, a helical spring  317 , a ferrule housing  355 , and an inner housing  320 . The ferrule housing  355  includes a front tube portion  350  connected with a rear tube portion  336  via a press-fit connection  337 . At the press-fit connection  337 , the rear tube portion  336  has a smaller outside diameter than the front tube portion  350  such that the rear tube portion  336  is received in the front tube portion  350 . The overlap of the front tube portion  350  relative to the rear tube portion  350  is limited by a flange  351  extending radially outward from an outer surface of the rear tube portion  350 . At a rearward side of the flange  351  (i.e., on an opposite side of flange  351  relative to the front tube portion  350 ), the outer surface of the rear tube portion  350  may include an annular groove  353 . 
     The ferrule basket  316  has a base  315  and a cylindrical stem  322  that extends from the base  315  in an axial direction away from the ferrule  314  towards the rear tube portion  336 , which is used to make a crimp connection around the optical fiber cable sheathing  112 . The spring  317  is seated around a portion of the stem  322  between an annular shoulder  324  on the stem  322  and an annular surface  352  within a cylindrical recess  354  defined by an inwardly-extending wall  359  of the flange  351  at a rearward end of the front tube portion  350 . The stem  322  slidably extends through an opening  339  at a forward end of the front tube portion  350 . A rearward end of the stem  222  is spaced from the inwardly-extending wall  359 , thereby permitting a degree of pivoting movement between the ferrule basket  316  and the ferrule housing  355 . 
     The ferrule basket  316  is configured to be inserted axially into the recess  354  of the front tube portion  350 . A top surface of the base  315  has a radially-extending protrusion  362  near a forward end of the ferrule basket. A top surface of the front tube portion  350  has an axially-extending longitudinal slot  356  configured to slidingly receive the protrusion. The aforementioned arrangement permits a degree of axial movement of the ferrule basket  316  and ferrule  314  relative to the front tube portion  350  of the ferrule housing  355 , with movement being therefore limited in one direction by the compression of the spring  317  between the two annular surfaces  324 ,  352  and in the other axial direction by the contact of the protrusion  362  with a forward end wall  357  of the slot  356 . 
     As shown in  FIGS.  10 - 12   , the inner housing  320  has a forward portion  330  that coaxially extends around the axially projecting ferrule  314  to define a receptacle  332  for a socket (not shown) configured to receive a projecting portion of the ferrule  314 . The ferrule basket  316  is free to move backwards inside the front tube portion  350  and the inner housing  320  when an end face  334  of the ferrule  314  comes into contact with a similar end face (not shown) of another optical fiber ferrule when making an optical connection. 
     The front tube portion  350  of the ferrule housing  355  may include a longitudinal notch  370  in its bottom outer surface that is keyed to an axially-extending projection  374  on the bottom inner surface of the inner housing  320  to prevent the ferrule housing  355  from rotating relative to the inner housing  320 . A rearward end of the receptacle  332  is bounded by a wall portion  333  having an opening  335  with a dimension that is smaller than a cross-sectional dimension of the receptacle  332 . The projection  372  extends rearward from the wall portion  333  and radially inward from an inner wall  329  of the inner housing  320 . As a result of the aforementioned structures of the projection  372  and the notch  370 , the inner housing  320  and the ferrule housing  355  are rotatably coupled to one another. As the inner housing  320  is slipped over the ferrule housing  355 , the notch  370  is aligned with the projection  372 . The ferrule housing  355  has a central aperture  357  through which the optical fiber  108  and buffering  110  pass, and has in a rear-most portion the rear tube portion  336  configured to receive and be crimped to the cable sheathing  112 . A boot  390  is provided around the junction of the optical fiber cable  102  and the ferrule housing sub-assembly  304  and includes at least one projection  392  extending radially outward and configured to be receiving in an opening  341  in an outer housing  340  to interlock the boot  390  with the outer housing  340 . 
     The outer housing  340  may be press-fitted axially over the assembled ferrule housing sub-assembly  304 . Once the inner housing  320  and outer housing  340  are engaged together, the inner and outer housings are relatively moveable with respect to each other along the ferrule axis  305  between limits defined by an interaction between the inner housing  320  and the outer housing  340  provided by projections  342  on a pair of opposite sides of the inner housing  320  and a pair of apertures  344  in the outer housing. The projections  342  and apertures  344  interact with spring features inside a matching socket (not shown) to provide SC-style push/pull engagement/disengagement configured to mate with an optical fiber socket. 
     The rotational orientation of the front tube portion  350  is set to one orientation relative to the ferrule  314  in the ferrule basket  316  owing to the cooperation between the protrusion  362  and the slot  356 . In this way, a first rotational key is provided between the ferrule basket  316  and the front tube portion  350  such that the ferrule basket  316  and the front tube portion  350  are rotatably fixed to one another (i.e., are not rotatable relative to one another). The optical fiber  108  is therefore terminated in a sub-assembly referred to herein as an optical fiber connector sub-assembly  360 . The resulting optical fiber connector sub-assembly  360  is therefore mechanically whole or integral, both as regards the components forming the sub-assembly and as regards the mechanical connection of the sub-assembly to the optical fiber cable  102 . 
     After the insertion has been performed, the assembly of the SC-type optical fiber connector  300  is completed as follows. The inner housing  320  is slid in an axial direction over the projecting ferrule  314  and surrounding front tube portion  350 . The inner housing  320  includes latches  321  on opposite side walls  323 . For example, the latches  321  may be disposed in cutouts  325  in the side walls  323  of the inner housing. The latches  321  may extend rearward from a forward wall  329  of the cutouts  325 . When the inner housing  320  is slid over the front tube portion  350 , the latches  321  are configured to deflect outwardly and when the annular groove  353  of the ferrule housing  355  reaches the latches  321 , the latches  321  move inwardly toward the annular groove  353  to a position in the annular groove  353 , thereby fixing the position of the ferrule housing  355  relative to the inner housing  320 . The external shape of the inner housing  320  where this interacts with the outer housing  340  is the same as or similar to conventional connectors. The outer housing  340  therefore is snap-fitted over the inner housing  320 , after which the SC-type connector  300  is fully compatible with conventional connectors and conventional optical fiber sockets. 
     The disclosure therefore provides a convenient optical fiber connector and optical fiber communication system and method for providing such a system. 
     Additional embodiments include any one of the embodiments described above, where one or more of its components, functionalities or structures is interchanged with, replaced by or augmented by one or more of the components, functionalities, or structures of a different embodiment described above. 
     It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present disclosure and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims. 
     Although several embodiments of the disclosure have been disclosed in the foregoing specification, it is understood by those skilled in the art that many modifications and other embodiments of the disclosure will come to mind to which the disclosure pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. It is thus understood that the disclosure is not limited to the specific embodiments disclosed herein above, and that many modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although specific terms are employed herein, as well as in the claims which follow, they are used only in a generic and descriptive sense, and not for the purposes of limiting the present disclosure, nor the claims which follow.