Abstract:
A fiber optic adaptor is provided which facilitates the connection of either an ST-terminated fiber or an FC-terminated fiber to another FC-terminated fiber, or to some other optical device. The adaptor has a pair of pins mounted on supports connected to an FC coupling receptacle. The pins have extended and retracted positions. When extended, the pins engage the J-shaped slots of the ST-terminated fiber, and when retracted, they are out of the way allowing the FC-terminated fiber to be connected to the receptacle. In another embodiment, an adaptor is provided which facilitates the connection of either an ST-terminated fiber or an SC-terminated fiber to another SC-terminated fiber.

Description:
FIELD OF THE INVENTION 
     The invention relates to optical fiber couplers and more particularly to optical fiber couplers which are mountable. 
     BACKGROUND OF THE INVENTION 
     In order to connect one optical fiber to another, the fibres to be connected are equipped with connectors at their ends. There are many types of such connectors, the most commonly used in North American telecommunications applications being AT&amp;T&#39;s (American Telephone and Telegraph) ST-type connector, and NTT&#39;s (Nippon Telegraph and Telephone) FC-type connector. Two fibres which are to be connected are equipped with the same type of connector (FC or ST), and these connectors are each connected to an intermediate optical fibre coupler (sometimes referred to as a coupling receptacle in the case of like connectors or a coupling adaptor in the case of connectors of two different types). A common requirement for any interconnection of optical fibres is that the connector ferrules be cleaned periodically because even a small amount of dust can interfere with optical signal propagation. 
     It is common to employ optical fibre couplers mounted in a panel forming part of an equipment enclosure thereby facilitating the interconnection of an external optical fibre to an internal fibre inside the enclosure connected to other internal equipment. There are several problems with the available techniques for mounting such optical fibre couplers. Such optical fibre couplers are typically mounted in a hole in the panel with a pair of screws which are difficult to undo. Even after such screws are removed, and the optical fibre coupler is removed, the internal fibre and its connector is still inside the enclosure and it is difficult to access the connector through the hole in the panel because such holes are conventionally smaller in diameter than the diameter of the connector terminating the internal fibre. This makes it very difficult to clean the connector of the internal fibre. 
     To alleviate these problems special design enclosures have been proposed (see U.S. Pat. Nos. 5,127,082 to Below et al which issued Jun. 30, 1992, 5,613,030 to Hoffer et al which issued Mar. 18, 1997) and optical fibre buildout systems have been proposed (see U.S. Pat. Nos. 5,067,783 to Lampert which issued Nov. 26, 1991, 5,717,801 to Smiley which issued Feb. 10, 1998, 5,073,042 to Mulholland et al which issued Dec. 17, 1991, and 5,274,729 to King et al which issued Dec. 18, 1993). These solutions are not very cost effective. 
     It may also periodically be a requirement to remove such an optical fibre coupler from a panel in order to replace it with a different type of optical fibre coupler, or to insert a bulkhead fibre optic attenuator for example. This task is also made difficult by conventional optical fibre coupler mounting techniques. 
     It is noted that both FC and ST-type connectors rely on a ferrule to achieve precise fibre alignment, but they employ different and incompatible latching mechanisms. The ST-type connector relies on a ¼ turn bayonet (spring loaded twist and lock) coupling mechanism, and the FC-type connector relies on a threaded coupling mechanism. In order to interconnect two fibres which are terminated with different connector types, for example an FC-terminated fibre and an ST-terminated fibre, special adaptors are required. 
     The most commonly used fibre connectors in local area communications include the SC-type connector and the above identified ST-type connector. Again, these connectors use different and incompatible latching mechanisms with the ST-type connector relying on the above identified ¼ turn bayonet coupling mechanism, and the SC-type connector relying on a push-pull coupling mechanism. 
     Applicant&#39;s copending U.S. application Ser. No. 09/019,508 Filed Feb. 5, 1998, hereby incorporated by reference, discloses couplers to facilitate the interconnection of different connector types. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a mechanism for mounting optical fibre couplers which facilitates their removal. 
     According to a first broad aspect the invention provides an optical fibre coupler mountable to a panel surface having a central hole, the coupler comprising: a first receptacle capable of receiving a first optical fibre connector of a first type; a second receptacle capable of receiving a second optical fibre connector of a second type, the first and second receptacles providing an optical interconnection between the first and second optical fibre connectors when connected; a bushing between said first and second receptacle having a mating surface on a side towards said first receptacle for abutment against the panel surface; at least two parallel pins permanently mounted in said bushing which extend from said mating surface; whereby the coupler is mountable to the panel by inserting the first receptacle through the central hole and by inserting and frictionally removably retaining the at least two pins in pin receiving holes correspondingly located on the panel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be described with reference to the attached drawings in which: 
     FIGS. 1A and 1B are a side view and an end view respectively of a conventional FC-terminated fibre; 
     FIGS. 2A and 2B are a side view and an end view respectively of a conventional panel mountable optical fibre coupler for FC-type connectors; 
     FIG. 2C is a plan view of a panel for receiving a optical fibre coupler of FIG. 2A; 
     FIGS. 3A and 3B are a side view and an end view respectively of a conventional ST-terminated fibre; 
     FIGS. 4A and 4B are a side view and an end view respectively of a conventional panel mountable optical fibre coupler for ST-type connectors; 
     FIGS. 5A and 5B are a side view and an end view respectively of an SC-terminated fibre; 
     FIGS. 6A and 6B are a side view and an end view respectively of a conventional panel mountable optical fibre coupler for SC-type connectors; 
     FIGS. 7A,  7 B and  7 C are perspective views of three different types of optical fibre couplers; 
     FIG. 8A and 8B are a side view and an end view respectively of an FC—FC optical fibre coupler according to an embodiment of the invention; 
     FIG. 9 is a plan view of a panel for use with the optical fibre couplers of FIGS. 8A; 
     FIGS. 10A and 10B are a side view and an end view respectively of an FC—FC optical fibre coupler according to another embodiment of the invention; 
     FIG. 11 is a plan view of a panel for use with the optical fibre couplers of FIG. 10A; 
     FIGS. 12 and 13 are side views of ST—ST optical fibre couplers according to further embodiments of the invention; 
     FIGS. 14 and 15 are side views of SC—SC optical fibre couplers according to further embodiments of the invention; 
     FIGS. 16 and 17 are side views of ST—SC optical fibre couplers according to further embodiments of the invention; 
     FIGS. 18 and 19 are side views of FC—ST optical fibre couplers according to further embodiments of the invention; 
     FIGS. 20 and 21 are side views of FC—SC optical fibre couplers according to further embodiments of the invention; 
     FIG. 22 is a side view of an adapted optical fibre coupler for use in connecting an FC-type connector to an ST-type connector or an FC-type connector according to an embodiment of the invention; 
     FIG. 23 is an end view of the adapted optical fibre coupler of FIG. 22; 
     FIG. 24 is a side view of an FC-terminated fibre connected to an FC-terminated fibre using the apparatus of FIG. 22; 
     FIG. 25 is a side view of an FC-terminated fibre connected to an ST-terminated fibre using the apparatus of FIG. 22; 
     FIG. 26 is a side view of an adapted optical fibre coupler for ST and SC-type connectors according to an embodiment of the invention; 
     FIG. 27 is a side view of two SC-terminated fibres connected using the apparatus of FIG. 26; and 
     FIG. 28 is a side view of an SC-terminated fibre connected to an ST-terminated fibre using the apparatus of FIG.  26 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A conventional FC-type connection is made between two FC-terminated fibres each such as the one illustrated in FIGS. 1A (side view) and  1 B (end view) through the use of an FC—FC panel mountable optical fibre coupler for FC-type connectors such as the one illustrated in FIGS. 2A (side view) and  2 B (end view). The FC-terminated fibre of FIGS. 1A and 1B has an FC-type connector generally indicated by  10  at the end of a fibre  12 . The FC—FC optical fibre coupler of FIGS. 2A and 2B is generally indicated by  29  and has at opposite ends a first receptacle  30  and a second receptacle  32  each of which are FC receptacles capable of receiving a FC-type connector. Between the two receptacles  30 ,  32  is coupling bushing  33  having two holes  34 , 36  on opposite diagonal corners. A corresponding panel designed to receive the connector  29  is shown by way of example in FIG.  2 C and is generally indicated by  40 . The term “panel” as used herein refers to any surface in which is to be mounted any optical fibre coupler. Furthermore, it is to be understood that any optical fibre coupler described herein provides an optical interconnection between the two receptacles of the optical fibre coupler, and more particularly provides an optical interconnection between any two connectors installed in the receptacles. The panel  40  has a central hole  42  of a diameter sufficient to receive the receptacle  30 , and has two threaded holes  44 , 46  which are located in correspondence with the holes  34 , 36  of the coupling bushing  33 . The optical fibre coupler  29  can be retained in the panel  40  by inserting the first receptacle  30  into hole  42  until the coupling bushing  33  abuts against the panel  40  and by screwing two screws through holes  34 , 36  into holes  44 , 46 . 
     A conventional ST-type connection is made between two ST-terminated fibres each such as the one illustrated in FIGS. 3A (side view) and  3 B (end view) through the use of an ST-ST optical fibre coupler for ST-type connectors such as the one illustrated in FIGS. 4A (side view) and  4 B (end view). The ST-terminated fibre of FIGS. 3A and 3B has an ST-type connector generally indicated by  50  at the end of a fibre  52 . The optical fibre coupler of FIG. 4A is generally indicated by  69  and has a first receptacle  70  and a second receptacle  72  each of which are ST receptacles capable of receiving an ST-type connector. Between the two receptacles is a coupling bushing  33  which is the same in shape and function as that of FIG. 2A again having two holes  34 ,  36 . There may also be a central outside threaded portion  75  which can be threaded into any correspondingly inside threaded item. The optical fibre coupler  69  may be mounted to a panel such as panel  40  of FIG. 2C in the same manner as described previously respecting optical fibre coupler  29  of FIG.  2 A. 
     A conventional SC-type connection is made between two SC-terminated fibres each such as the one illustrated in FIGS. 5A (side view) and  5 B (end view) through the use of a SC-SC optical fibre coupler for SC-type connectors such as the one illustrated in FIGS. 6A and 6B. The SC-terminated fibre of FIGS. 5A and 5B has an SC-type connector generally indicated by  90  at the end of a fibre  92 . The optical fibre coupler of FIGS. 6A and 6B is generally indicated by  109  and has a first receptacle  110  and a second receptacle  112  each capable of receiving an SC-type connector. Between the two receptacles is a coupling bushing  33  which is the same in shape and function as that of FIG. 2A again having two holes  34 ,  36 . The optical fibre coupler  109  may be mounted to a panel such as panel  40  of FIG. 2C in the same manner as described previously respecting optical fibre coupler  29  of FIG. 2A, although the central opening  42  would need to be appropriately sized to receive the rectangularly shaped optical fibre coupler  112 . 
     Three further conventional optical fibre couplers are shown in FIGS. 7A,  7 B and  7 C. The optical fibre coupler of FIG. 7A is designed to couple an ST-terminated fibre to an SC terminated fibre. The optical fibre coupler of FIG. 7B is designed to couple an FC-terminated fibre to an ST terminated fibre. The optical fibre coupler of FIG. 7C is designed to couple an FC-terminated fibre to an SC terminated fibre. 
     It is noted that any of the optical fibre couplers described above respecting FIGS.  2 , 4 , 6 , 7  may also be implemented to include a built-in attenuation function. 
     Referring now to FIGS. 8A (side view) and  8 B (end view) a FC—FC optical fibre coupler according to an embodiment of the invention is shown, generally indicated by  200 . As in the prior art FC—FC coupling bushing of FIG. 2, the coupler  200  has two receptacles  30 , 32  for receiving FC-terminated fibre connectors. There is a bushing  202  and two spring tension pins  204 , 206  mounted in holes on opposite diagonal corners of the bushing. The bushing  202  is made with two holes of a size to receive and permanently frictionally retain the two spring tension pins  204 , 206 . 
     A panel according to an embodiment of the invention for use with the optical fibre coupler of FIG. 8 is illustrated in FIG.  9  and is generally indicated by  210 . It includes a central hole  212  for receiving the receptacle  30 , and has two holes  214 , 216  sized to receive and frictionally removably retain the two spring tension pins  204 , 206 . 
     The spring tension pins may for example be ISO 8752 series pins (manufactured by Spaenaur for example) which have a nominal diameter of 2.0 mm, an outside diameter of 2.3 mm before insertion, and a recommended hole size of 2.1 mm. In this case, the holes for the spring tension pins  204 ,  206  in the bushing would be 2.0 mm in diameter and the holes  214 ,  216  in the panel would be 2.1 mm in diameter. Other spring tension pins may of course alternatively be used. 
     Referring now to FIGS. 10A (side view) and  10 B (end view) a FC—FC optical fibre coupler according to another embodiment of the invention is shown, generally indicated by  220 . As in the prior art FC-FC coupling bushing of FIG. 2, the coupler  220  has two receptacles  30 , 32  for receiving FC-terminated fibre connectors. There is a bushing  222  and two locking pins  224 , 226  on opposite diagonal corners of the bushing. The locking pins  224 , 226  may be installed by pressure fitting them in holes in the bushing  222 . Each locking pin includes a narrow portion  224 A, 226 A and an end portion  224 B, 226 B. 
     A panel according to an embodiment of the invention for use with the optical fibre coupler of FIG. 10A is illustrated in FIG.  11  and is generally indicated by  230 . It includes a central hole  232  for receiving the receptacle  30 , and has two openings generally indicated by  234 , 236 . The openings  234 , 236  have large opening portions  238 , 240  sized to receive the end portions  224 B, 226 B of the locking pins, and engaging portions  242 , 244  sized to frictionally retain the locking pins  224 , 226  of the optical fibre coupler of FIG.  10 . The frictional retention is achieved through friction between the engaging portions  242 , 244 , and the narrow portions  224 A, 226 A of the locking pins  224 , 226 . To install the optical fibre coupler, the locking pins  224 , 226  are inserted into portions  238 , 240 , and the receptacle is rotated such that the locking pins move into the engaging portions  242 , 244 . 
     In a preferred embodiment, the central hole ( 212 , 232 ) in either of the above embodiments in the panel is larger than hole  42  in conventional panels (see FIG.  2 C), and more particularly is of a diameter large enough to pass an FC-type connector (see FIG. 1) through the hole. Conventional FC-type connectors typically have a diameter of 10.0 mm, and as such, a preferred diameter for the central hole is 10.1 mm. More generally, the diameter should be at least 0.1 mm larger than the diameter of the connector to be passed through. 
     The optical fibre couplers of FIGS. 8A and 10A are easily removable for cleaning or exchanging purposes. When used in combination with the preferred panel having a large central opening, the optical fibre coupler can be removed, and the interior connector pulled through the central opening for easy cleaning. 
     An ST-ST optical fibre coupler equipped with spring tension pins according to an embodiment of the invention is shown in FIG.  12 . An ST—ST optical fibre coupler equipped with locking pins according to an embodiment of the invention is shown in FIG.  13 . The central threaded portion is not necessary in these embodiments. 
     An SC—SC optical fibre coupler equipped with spring tension pins according to an embodiment of the invention is shown in FIG.  14 . An SC—SC optical fibre coupler equipped with locking pins according to an embodiment of the invention is shown in FIG.  15 . 
     An ST—SC optical fibre coupler equipped with spring tension pins according to an embodiment of the invention is shown in FIG.  16 . An ST—SC optical fibre coupler equipped with locking pins according to an embodiment of the invention is shown in FIG.  17 . 
     An FC—ST optical fibre coupler equipped with spring tension pins according to an embodiment of the invention is shown in FIG.  18 . An FC—ST optical fibre coupler equipped with locking pins according to an embodiment of the invention is shown in FIG.  19 . 
     An FC—SC optical fibre coupler equipped with spring tension pins according to an embodiment of the invention is shown in FIG.  20 . An FC—SC optical fibre coupler equipped with locking pins according to an embodiment of the invention is shown in FIG.  21 . 
     Referring to FIG. 22, in another embodiment of a FC—FC optical fibre coupler, in addition to the features of the optical fibre coupler of FIG. 8, adaptor pin supports in the form of arms  300 , 302  protrude at right angles from the bushing  202  and on opposite sides of the bushing  202 . Each arm  300 , 302  has a respective retractable adaptor pin  304 , 306 . These adaptor pins  304 , 306  are described in detail below. An optical fibre coupler including such arms and pins will be referred to as an adapted optical fibre coupler and is generally indicated by  301 . The retractable adaptor pins  304 , 306  in FIG. 22 are in their extended position, while the same adaptor pins are shown in FIG. 23 (end view) in their retracted positions. The adapted optical fibre coupler  301  of FIG. 23 is now capable of being used to connect a pair of FC style connectors, or an FC connector and an ST connector. 
     In FIG. 24, the adapted optical fibre coupler  301  is used to connect two FC-type connectors  310 , 312 . In this configuration, the adaptor pins  304 , 306  are moved to their retracted position, and the adapted optical fibre coupler functions in its normal mode. In FIG. 25, the adapted optical fibre coupler  301  is used to connect an FC-type connector  310  to an ST-type connector  314 . In this configuration, the adaptor pins  304 , 306  are moved to their extended position. One of the two receptacles of the adapted optical fibre coupler functions in its normal mode to couple to the FC-type connector  310 . On the other side, the ferrule of the ST connector  314  is inserted inside the inner cylinder of the remaining FC receptacle  32 . The inner cylinder of the receptacle  32  butts against the inner cylinder of the connector  314 , and the spring loaded outer portion  60  is pressed towards the adapted optical fibre coupler  301  so as to receive the two adaptor pins  304 , 306  in its J-shaped notches. The spring loaded outer portion  60  is then rotated to catch the pins  304 , 306  in the end portions of the J-shaped notches  62 . 
     The necessity for the adaptor pins  304 , 306  to engage the J-shaped notches  62  of the ST-type connectors imposes requirements upon the dimensions of the optical fibre coupler. It is important that the adaptor pin supports  304 , 306  be connectable to the FC receptacle in a manner which supports the pins in positions perpendicular to the longitudinal axis of the receptacle and on opposite sides of the receptacle such that they do not interfere with the connection of an FC-type connector to the FC receptacle when they are in their retracted position. It is also important that the adaptor pins when extended are capable of engaging the J-shaped notches of an ST-type connector. 
     There are many ways to implement the adaptor pins  304 , 306 . The adaptor pins may be implemented as a pair of spring pins which are biased towards their extended positions but which may be compressed to their retracted positions. The adaptor pins may be implemented with a pair of screws which can be screwed into the arm portions to their extended positions, or partially unscrewed from the arm portions to their retracted positions. 
     In another example the adaptor pins may be provided with first and second spaced ring notches within which to receive a ball bearings which are spring loaded within the arms in which they are mounted. 
     The arm portions may be separate pieces initially from the bushing or may be integrated all as one unit. 
     The embodiment of FIGS. 22-25 features spring tension pins to enable mounting the optical fibre coupler to a panel  400 . Of course, alternatively, locking pins may be used, provided the corresponding receiving holes exist in the panel  400 . 
     Referring now to FIG. 26, one of the two SC-type receptacles  320 , 322  of the SC—SC type optical fibre coupler of FIG. 14 has been adapted according to an embodiment of the invention to permit either an SC—SC connection or an SC—ST connection. In this case, the outer rectangular portion of the adapted receptacle  322  has been shortened. Two adaptor pin supports  300 , 302  retractable adaptor pins  304 , 306  preferably are integrated with the bushing  202 . It is important that the adaptor pin supports  300 , 302  be connectable to the SC receptacle in a manner which supports the adaptor pins in positions perpendicular to the longitudinal axis of the receptacle and on opposite sides of the receptacle such that they do not interfere with the connection of an SC-type connector to the SC receptacle when they are in their retracted position. It is also important that the adaptor pins when extended are capable of engaging the J-shaped notches of an ST-type connector. With the adaptor pins  304 , 306  retracted, a normal SC—SC connection may be made such as illustrated in FIG.  27 . With the adaptor pins  304 , 306  extended, an SC—ST connection may be made such as illustrated in FIG.  28 . 
     The embodiment of FIGS. 26-28 features spring tension pins. Of course, locking pins could alternatively be used. 
     Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein. 
     While in the above described embodiments, the interface between the optical fibre coupler and the panel has included a pair of flat surfaces, more generally, the panel will have a surface, and the optical fibre coupler will have a corresponding mating surface. 
     Preferably the spring tension pins or locking pins extend perpendicular to the bushing but this is not essential provided the holes in the panel are correspondingly angled. While two spring tension pins (or two locking pins) have been used in the examples, of course additional pins may be used. 
     Three types of receptacles, namely FC, ST and SC have been considered in the above examples. Of course, the invention may be applied to either receptacle types.