Connector and receptacle containing a physical security feature

[0001] This application claims priority to U.S. Provisional Application No. 60/218,705, filed Jul. 17, 2000.

[0002] The present invention relates to connectors for the use with fiber optics, and more specifically relates to a system of novel key-slot structures to provide several mutually exclusive connectors for discriminating between users.

[0003] Fiber optic communication systems have become increasing more popular in recent years. Fiber optic technology provides several advantages over the conventional copper wire-based technology. For example, fiber optic communication systems provide substantially increased bandwidth and allow for large volumes of data to be transferred quickly over long distances. In addition, these communications systems are not susceptible to electromagnetic interference (EMI).

[0004] With the increase in use of fiber optic systems, connectors have become necessary for connecting separate fiber optic cables. Connecting independent fiber optic cables can be challenging due the nature of optical fiber. For example, it is important that the optical fibers being connected are aligned properly in the axial and transverse directions so that there is minimal loss of light, i.e., data, at the connection.

[0005] As the fiber optic field has grown, there has been much effort devoted to developing various connectors to meet the needs of fiber optic systems. Connectors such as the SC Type connector and ST type connector became widely used as the industry standard. These types of connectors attempt to provide accurate and precise connection between fiber optic cables.

[0006] While fiber optic systems first gained acceptance as the backbone of many network systems, copper wire technology was still the most prevalent manner of connecting various workstations to the network system. Recently, however, the use of fiber optic technology has been extended to the complete network system including workstations, often referred to as fiber-to-the-desk (FTTD) applications.

[0007] The growth of FTTD applications complicates the requirements of optical connectors. In particular, connectors are needed that are small enough to be used in an office environment and that can be easily installed in the field. A group of connectors were developed to meet this need and are known as Small Form Factor (SFF) connectors. SFF connectors are designed to be the fiber optic equivalent of the small connectors used in copper wire technology, such as, for example, RJ-45 connectors. These small, efficient, easy-to-use SFF connectors have become a new industry standard and are expected to contribute to the continued growth of FTTD applications. One SFF connector of particular interest herein is the MT-RJ connector. Details on the construction of this type of connector can be found in U.S. Pat. No. 6,224,268, issued to Manning.

[0008] The increased popularity of FTTD applications creates a new problem as many large networks implement SFF connectors such as the MT-RJ connector. That is, a need has developed to limit user access to the particular fiber optic networks for security or other reasons. While some access limitation can be obtained through the use of software (e.g., passwords), further limitations are desirable using some type of physical barrier to the networks.

[0009] Therefore, what is desired is a means to regulate access to a network using some kind of physical barrier to prevent unauthorized users from connecting to the network.

[0010] The present invention provides for a connector system that provides discriminating mating between plugs and receptacles by using a system of geometrically matched connector components which allow certain pairs of connectors to mate but which prevent all other combinations of connectors to mate.

[0011] In a preferred embodiment, the connector system comprises (a) a plurality of receptacles, each receptacle having an inner surface with a first geometry; (b) a plurality of plugs, each plug having a second geometry; (c) wherein the second geometry of a plug cooperates with at least one first geometry of a receptacle to allow the plug and the at least one receptacle to mate, while the second geometry of the plug physically interfering with all other second geometries of all of the other receptacles of the plurality of receptacles to prevent mating therewith.

[0012] Preferably, the receptacle is a jack having a tub and the first geometry comprises a key and a plurality of ribs extending inward, and the plug comprises a housing and a ferrule contained within the housing, wherein the second geometry comprises a slot in the housing for cooperating with the key and secondary slots for cooperating with the ribs, and wherein the slot and the secondary slots cooperate with the key and the ribs to effect pre-alignment of the ferrule before final mating of the ferrule.

[0019] The present invention relates to a connector system comprising a series of connector components which interconnect with each other in a discretionary way. Referring to FIG. 1, a preferred embodiment of a mating plug 101 and receptacle 100 of the connector system is illustrated. As shown, the plug 101 is partially inserted into the receptacle 100, which, in this embodiment, is a jack having a tub portion 102. Although a jack is discussed herein in detail, it should be understood that the receptacle of the present invention is not restricted to a jack and may be any structure configured to receive a plug, including, for example, an adapter for connecting two plugs together or an integral connector on an active device (e.g., transceiver) or passive device (e.g., splitter).

[0020] The plug typically contains a conductive element such a fiber or wire which mates with a similar element in the receptacle. In fiber optic applications, it is common for the conductive element to be contained in a ferrule, which in turn is housed by the plug. In a preferred embodiment, the ferrule is an MT-type ferrule.

[0021] The outer surface of the plug 101 and the inner surface of the tub 102 have first and second geometries, respectively, which cooperate to allow only certain pairs of plugs and receptacles to mate (herein “mating pairs,” “mating plug and jack,” or “keyed pair”), and which physically interfere for all other combinations of plugs and jacks (herein “non-mating pairs,” “non-mating plugs and jacks” or non-keyed pairs), thereby preventing non-mating plugs and jacks from effecting an optical or electrical coupling.

[0022] The first and second geometries may embody any known keying mechanism which discriminates between connector components. Such keying mechanisms include, for example, a key and slot relationship between the plug and jack, a receptacle dimensioned to receive only certain sized or shaped plugs, and even a magnetic signature for either attracting (for mating pairs) and repulsing (non-mating pairs). Preferably, the keying mechanism involves just a slight modification to the plug and jack such that essentially the same molds can be used to manufacture connectors of different keyed pairs. Although molding is preferred, it is should be understood that other techniques for producing the first and second geometries can be used including, for example, over molding and machining.

[0023] In a preferred embodiment, the invention uses a key and slot mechanism. Specifically, the slot can be embodied in the first or second geometry and the key can be embodied in the other geometry. In the particularly preferred embodiment shown in FIGS. 1-4, the key is part of the second geometry, while the slot is part of the first geometry; that is, the plug 101 has a slot 103 and the tub portion 102 of the jack has a key 104.

[0024] This configuration is preferred since the key may cooperate with other “ribs” on the connector for pre-alignment purposes. More specifically, with particular reference to FIG. 3, an end view of housing 301 of the plug 101 is shown. The housing comprises four walls each wall having a slot 103, 302a, 302b, and 302c, respectively. FIG. 4 depicts an end view of housing 401 of the tub 400 in which the key 104 and ribs 402a, 402b, and 402c are disposed on the walls of the housing. The key 104 and the ribs 402a, 402b, and 402c cooperate with the slots 103, 302, 302a, 302b, and 302c, respectively, to effect pre-alignment of ferrule located within the plug with the jack before final mating of the connector plug with the connector jack. The final mating may be between the conductive elements of the connector system, such as, for example, between a couple of MT-type ferrules, which employ precise alignment pins/receiving holes on the ferrule face. Such ferrules are well known in the art. By pre-aligning the MT ferrules through the synergistic use of the key and slot, the inter-engagement of the closely-toleranced alignment pins/receiving holes is facilitated. The above-described synergistic keying and aligning feature of the present invention is realized with the MT-RJ connector (Tyco Electronics, Harrisburg, Pa.).

[0025] In a preferred embodiment, the mating end of the key 104 contains a flat portion shown as 105 and the mating end of the plug 101 has a chamfers 106 on the corners of the edges of the slot 103, while the remainder of the mating end of the plug comprises a flat portion 107. The radius comers on the key 106 and the chamfers on the plug 107 work as a guiding device and provide for the necessary alignment between the key and the slot when the plug is inserted into the tub of the jack. On the other hand, as shown in FIG. 2, when a user attempts to mate two non-mating plug and jack components, the flat portion of the key 105 contacts the flat portion of the plug 107 and provides for definite physical interference between the plug and jack when slot and key do not correspond. Accordingly, the use of this geometry prevents a user from forcing two non-mating plugs and jacks together. Therefore, the physical interference provided between the flat portion 105 of the tub and the flat portion 107 of the key assures that only desired combinations of plugs and jacks will mate.

[0026] The position of the key 104 on the tub 102 and the slot 103 on the plug 101 can be varied in such a manner so that a plurality of mutually-exclusive slot and key positions are formed. In one embodiment, the series of key and slot locations are mutually exclusive so that there is a one-to-one correspondence between jacks and plugs. In another embodiment, certain plugs may be configured to mate with a variety of different jacks. For example, it may be worthwhile to give network administers or people with high security clearance certain “master” plugs which are capable of mating with a number of jacks having different slot positions. Referring to the figures, FIG. 5 shows an embodiment of a master plug 501 which has a slot 502 that is configured (which, in this embodiment, means it is wide enough) to mate with jacks 503 and 504 which have different key positions 505 and 506, respectively. Although a wide slot is used in this embodiment to effect mating with two or more jacks having different key configurations, it should be understood that other embodiments are possible, such as, for example a plug with two or more slots.

[0027] The number of possible mutually exclusive mating pairs for a given plug and receptacle is a function of the physical parameters of the plug and the receptacle. More specifically, with reference to FIGS. 1-4, mutual exclusivity is ensured by adhering to the following relationships:
X₁−C/2(D−A)+Δ≦F/2  (1)
X₂+B/2<A/2−W  (2)
X_1a+Clear₁+Z=X_1b  (3)
wherein:

• • [0028] A=the width of the plug 101;
  • [0029] B=the width of the slot 103 onthe plug 101;
  • [0030] C=the width of the key 104;
  • [0031] D=the distance across the opening of the tub;
  • [0032] F=the width of the ferrule residing within the plug;
  • [0033] Δ=CL_F−CL_A, wherein
    • [0034] CL_A=centerline of the width of the plug; and
    • [0035] CL_F=centerline of the ferrule residing within the plug.
  • [0036] X₁=the distance from the center of the opening in the tub 102 to the center of the key 104 for each mutually exclusive position.
  • [0037] X₂=the distance from the center of the plug 101 to the center of the slot 103 for each mutually exclusive position;
  • [0038] X_1a=the X₁ distance for a sequentially first key in a series of connectors;
  • [0039] X_1b=the X₁ distance for a sequentially second key in a series of connectors;
  • [0040] W=the wall thickness of the plug housing
  • [0041] Z=the minimum distance required to ensure that the flat portion of the key does not contact the flat portion of the plug 107 when a user attempts to mate a mating pair;
  • [0042] Clear₁=the clearance distance between the center side of the key and the center side of the slot;

[0043] These relationships must be satisfied for the mating pairs to mate and for the non-mating pairs to definitely not mate. Specifically, for a mating pair, Relationship (1) requires that half the ferrule width must be no less than X₁ less one half of C added to the difference between the width of the tub opening D less the width of the plug added to the difference between the centerline of the ferrule within the plug and the centerline of the plug. This ensures that the key is not positioned outside of the area on which at least a portion of the ferrule will reside. By adhering to this parameters the key will have some overlap with the ferrule, and thus will provide for pre-alignment of the ferrule in the same manner as do the ribs on the three sides of the ferrule without the key.

[0044] Relationship (2) requires that X₂ added to one-half of dimension B is less than one-half of dimension A less W. This assures that the slot resides on the plug within the confines of the plug walls.

[0045] Finally, according to Relationship (3), for each mutually exclusive position, the distance X₁ for the first connector in the system (X_1a) added to Clear₁ added to a predefined interference interval Z would correspond to the distance X₁ for the next slot/key position (X_1b) Z is the minimum distance required to ensure that the flat portion of the key does not contact the flat portion of the plug 107 when a user attempts to mate the two portions of a connecter which is intended to mate.

[0046] By way of example, four mutually exclusive locations for locating the slot on the plug housing and the key on the tub are defined below for an MT-RJ connector. The MT-RJ connector has the following dimensions:

• • [0047] A=7.15±0.05 mm
  • [0048] B=1.25 mm
  • [0049] C=0.95±0.04 mm
  • [0050] D=7.24±0.04 mm
  • [0051] F=4.5±0.04 mm
  • [0052] Clear₁=0.15 mm
  • [0053] W=0.8 mm

[0054] Based on these MT-RJ dimensions, it has been found that the following X₁ key positions satisfy the relationships above:

[0055]

Mating pair	Key Position	X1
1	1	0.8	mm
2	2	1.6	mm
3	3	−0.8	mm
4	4	−1.6	mm

Although the data above indicates four mutually exclusive positions, it should be understood that additional positions are possible within the parameters of the MT-RJ connector. Additionally, it should be understood that the combinations of various key positions can be used to increase the number of permutations of mating pairs. For example, in addition to the four mating pairs listed above, additional mating pair configurations may obtained from the following combinations of key positions:

[0056]

Mating pair	Key Positions
5	1, 2
6	1, 2, 3
7	1, 2, 3, 4
8	2, 3
9	2, 4
10	2, 3, 4
11	3, 4
12	1, 3
13	1, 4
14	1, 3, 4
15	1, 2, 4

[0057] In a preferred embodiment, the key and slot components are combined with the industry standard MT-RJ connector. FIG. 6 and FIG. 7 show the key-slot combination added to the MT-RJ connector as produced by Tyco Electronics of Harrisburg, Pa.

[0058] FIGS. 6 (a)-(c) show the plug 602 of the MT-RJ connector combined with the slot 601 of the present invention. FIGS. 7(a) and 7(b) show the center tub portion 703 of an MT-RJ connector jack. The key is shown as 701 located in one of the plurality of possible positions. The three pre-alignment ribs are shown as 702a, 702b, and 702c. The key 701 functions as the discriminating member for allowing or preventing mating with a plurality of plugs, while at the same time functioning as the pre-alignment member for the remaining side of the ferrule not aligned with ribs 702a, 702b, and 702c.

[0059] To provide a simple and readily apparent indication to the user of which plugs mate with which receptacles, it is preferable to mark mating pairs with indicia or color to indicate their compatibility. In a preferred embodiment, the components of a mating pair are a similar color different from all others used in the connector system.

[0060] The system described allows for a series of mutually-exclusive connectors to be used in a manner which provides physical security to a network system. In light of the often highly sensitive data stored on many of the networks in use today, this is a highly desirable feature. The present invention is an effective way to segregate separate networks and assure that the proper users are connecting to the desired network. Additionally, the present invention may be employed in the manufacture of devices in which fibers or wires need to be connected in particular arrangements. More specifically, the discriminating connectors of the present invention can be engineered into a system such that, during manufacturing, the correct connection of the fibers/wires is ensured by the mating pairs and their ability to prevent all other “incorrect” connections. Applications requiring particular routing of fibers or wires include, for example, routers, backplane assemblies, and even component devices such as multiplexers/demultiplexers.

[0061] It should be understood that the foregoing is illustrative and not limiting and that obvious modifications may be made by those skilled in the art without departing from the spirit of the invention. Accordingly, the specification is intended to cover such alternatives, modifications, and equivalence as may be included within the spirit and scope of the invention as defined in the following claims.