HIGH-DENSITY OPTICAL CONNECTING BLOCK

[0001] This patent application is related to application Ser. No. ______ (Anderson 16-11-11), which is filed concurrently herewith.

[0002] This invention relates generally to a device for coupling optical fibers and, more particularly, to an apparatus that provides structural rigidity in panel-mounted applications and enables high-density optical fiber interconnections.

[0003] Optical fiber systems require that optical signals be routed to one destination and periodically re-routed to another destination. Such routing takes place at various locations along a transmission path. For example, Lucent Technologies has designed an optical switch that uses 256 or more movable mirrors to selectively route the paths of optical signals among a number of optical fibers that are coupled to the switch. The switch is generally administered through a connection panel that terminates a large number of optical fibers, each of which terminates in an optical plug. Coupling apparatus is installed in the panel for enabling interconnection between individual pairs of optical plugs.

[0004] One example of optical coupling apparatus is shown in U.S. Pat. No. 5,274,729 that issued on Dec. 28, 1993 in the names of King et al. The King et al. reference discloses a number of blocks that are adapted for mounting to a panel through a plurality of openings provided therein. The King et al. system further includes a number of buildouts, that are adapted to be removably attached to the blocks that are mounted on the connection panel. Each connecting block includes a front aperture that forms a keyway, which is adapted to align and receive a cylindrical boss that holds an alignment sleeve. And while the King et al. system functions adequately, demand for an increasing number of optical fiber connections has prompted the design of smaller optical fiber plug connectors that occupy less space.

[0005] U.S. Pat. No. 5,481,634 issued on Jul. 8, 1997 and discloses a low-profile, optical fiber plug connector. Its design is advantageous because it has a smaller footprint than any of its predecessor connectors and therefore requires less panel space. But while the development of the LC connector has shown that an optical plug connector can be successfully reduced in size, such size reduction is wasted unless the panel-mounted connecting hardware can accommodate an increased density of such reduced-size optical plugs.

[0006] An optical coupling apparatus that uses the LC plug connector is shown in U.S. Pat. No. 5,647,043, which discloses a jack receptacle that snaps into a connecting panel. The receptacle is fully assembled prior to panel mounting, which means that the type of optical plugs that can be used on the panel is fixed at the time of installation. And in order to accommodate the installation and removal of optical plugs, adjacent rows of optical ports are inverted with respect to each other in order to enable a user to operate the cantilever latches it may not be convenient to construct an array of jack receptacles having more than two rows since the optical plugs are inverted for accessibility to their latches. Such inversion may even lead to connection error in a situation where duplex optical connectors are used because the left-to-right orientation of the transmitting and receiving fibers is reversed between rows.

[0007] Accordingly, it is desirable to provide connecting hardware for use in a connection panel that enables high-density optical interconnections between optical plug connectors. Additionally, it is desirable that the connecting hardware accommodate duplex optical connectors, and that the duplex optical connectors accommodate different types of optical plugs. Finally, it is desirable that the connecting hardware have a uniform structure throughout so that left-to-right reversals of transmitting and receiving fibers are avoided when duplex connectors are used.

[0008] A high-density optical connecting block is designed to mount in a generally flat panel and includes a number of interlocked horizontal and vertical ribs that form an array of cells. The array includes at least twelve cells that are arranged in two or more rows and two or more columns. The front side of each cell includes recesses that are shaped to receive and interlock with a duplex optical connector.

[0009] In a preferred embodiment of the invention, each cell has a back side that is shaped to receive and interlock with a pair of individual optical plugs. Preferably, the connecting block is molded as a unitary structure from a polymeric material and includes thirty-six cells, which are disposed in three rows and twelve columns. Also, preferably, the connecting block includes keying features on opposite sides thereof so that when they are mounted side-by-side in a panel, adjacent connecting blocks can only be installed in one orientation.

[0010] In the illustrative embodiment, the front side of the connecting block further includes a pair of openings for receiving guide members that are positioned on the top and bottom sides of the duplex optical connector, and each opening includes a retaining surface molded therein for interlocking with the guide members on the duplex connector. Moreover, the openings are shaped to allow the duplex connector to fit into a cell in only one orientation. Illustratively, the vertical and horizontal ribs have a front-to-back depth that is greater than 10 millimeters for imparting flexural rigidity to the panel.

[0011] The invention and its mode of operation will be more clearly understood from the following detailed description when read with the appended drawing in which:

[0012] FIG. 1 shows an exploded perspective view of a panel-mounted connecting block receiving a duplex connector in its front side and individual optical plugs in its back side;

[0013] FIG. 2 is a front side perspective view of a preferred embodiment of the connecting block having 36 cells;

[0014] FIG. 3 discloses a front view of a pair of adjacent cells within the connecting block;

[0015] FIG. 4 discloses a back view of the pair of adjacent cells shown in FIG. 3;

[0016] FIG. 5 is a back-end perspective view of a duplex optical connector;

[0017] FIG. 6 is a front-end perspective view of the duplex connector;

[0018] FIG. 7 is a front-end view of the duplex connector;

[0019] FIG. 8 is a side cross-section view of the duplex connector; and

[0020] FIG. 9 is a partial cross-section view of the duplex optical connector of FIG. 8 having an optical plug inserted therein.

[0021] The present invention relates to the hardware used in making interconnections between optical plugs such as described above. As discussed above, panel-mounted connections were previously provided via individual buildout blocks and buildouts; or by mounting jack receptacles to a panel to receive small groups of optical plugs. However, such arrangements have: (i) involved far too many individual components that were manually assembled; (ii) have not imparted sufficient rigidity to the panel; and (iii) have not provided sufficient connection density. All of these drawbacks are overcome by the apparatus shown in FIG. 1, which includes a connecting block 100 and a duplex connector 50 that are suitable for use in a connecting panel 10.

[0022] FIG. 1 shows an exploded perspective view of an assembly comprising a panel-mounted connecting block 100, a duplex connector 50, and a number of optical plugs 20. The purpose of such an assembly is to centralize and administer interconnections between optical fibers. For example, one optical fiber is contained within optical cable 30-1 and another optical fiber is contained within optical cable 30-3. These cables respectively terminate in optical plugs 20-1 and 20-3. Connecting block 100 and duplex connector 50 facilitate the interconnection between these optical plugs. For the purpose of illustration, the optical plugs 20 shown in FIG. 1 are LC-type plug connectors of the type discussed above. Nevertheless, the present invention may be used with other known optical plugs as well as optical plugs not yet in existence. Each optical plug 20 comprises a generally rectilinear housing 22 having an opening through which a ferrule 21 protrudes. Each ferrule 21 contains a optical fiber (not visible) that extends from the tip of the ferrule, through the optical plug 20, to an optical cable 30. Each optical plug 20 is provided with a latching tab 25 that is positioned on its top side in order to interlock with an associated receptacle.

[0023] Panel 10 is provided with a number of elongated continuous slots 14-1, 14-2 that are adapted to accommodate one or more connecting blocks 100. Illustratively, the panel is made from relatively thin steel (e.g., about 2.3 millimeters). As shown, slots 14-1 and 14-2 are sized to receive a single connecting block 100, although it is contemplated that some or all of the horizontal bars in the panel 10 can be eliminated so that a number of connecting blocks can be stacked directly on top of each other. In that situation, it may be desirable to provide mating features (e.g., tabs and slots) on the top and bottom sides of each connecting block for improved rigidity.

[0024] The connecting block 100 is preferably molded from a resilient polymeric material such as polyetherimide (PEI) as a one-piece structure. It has a waffle-like structure of interlocked horizontal 150 and vertical 160 ribs, which form cells and provide structural integrity to the panel. The ribs 150, 160 have a front-to-back depth that is greater than 10 millimeters (mm). In a preferred embodiment of the invention, the ribs have a depth of about 13 mm. A flange 101 that circumscribes the connecting block further enhances rigidity. In the preferred embodiment, the flange has a front-to-back depth of about 6 mm. An important feature of the connecting block 100 is that it is constructed as an array of identical cells 110, each being substantially identical to the others in size, shape and orientation, and each being designed to receive a duplex connector in its front side. This is particularly advantageous because it is convenient to organize fibers into pairsone for each direction of transmission. Moreover, connecting block 100 provides accurate interconnections in a structure having relaxed tolerances. This is because dimensional accuracy is important within each cell to assure proper mating with a duplex connector, but not particularly important between cells.

[0025] Suitable interconnection density and flexural rigidity are provided when the cells of the connecting block number at least twelve and are arrayed into at least two rows and at least two columns. Each connecting block is held within a slot 14-1 in the panel 10 by fasteners such as screws and nuts (not shown) that fit through one or more eyelets 111, 122, 123 that are positioned on opposite sides of the connecting block 100. Mating holes 11 are provided in the panel 10 for receiving the screw. The eyelets and screws could be replaced by protrusions that are molded in the connecting block at similar locations. Additionally, recesses 112, 113, 121 are provided on opposite sides of the connecting block that are shaped to be intermatable with the eyelets when the connecting blocks are positioned side by side. Significantly, the eyelets and recesses are keyed to prevent adjacent connecting blocks from be installed improperly (i.e., upside down and/or reversed from front to back). It is noted that the connecting block 100 can be designed to avoid the need for auxiliary fastening hardware (e.g., screws and nuts) by molding wedge-shaped tabs in the region behind the eyelets and recesses that enable the connecting block 100 to be snapped into the panel slot 14-1.

[0026] The connecting block 100 is used in conjunction with a number of duplex connectors 50 that individually yoke a pair of simplex optical plugs 20-1, 20-2 into a duplex configuration. Each duplex connector 50 includes a pair of side-by-side optical ports 153-153, each port including internal walls that define a cavity. As illustratively shown in FIG. 1, the cavities are shaped to receive LC-type optical plugs 20-1 and 202. Each cavity further includes a tubular boss 58 that extends through a front wall of the cavity for receiving an optical fiber, which is contained within the ferrule 21. It is understood that when plastic fiber is used, ferrules are not needed because plastic fibers typically have a much larger diameter (i.e., about 1 mm) than a glass fiber, which has a diameter of only 125 microns. Nevertheless, when the optical plug has a ferrule containing a glass fiber, alignment between abutting ferrules is preferably accomplished via a cylindrical alignment sleeve 60, which is disposed within the boss 58 and dimensioned to receive a ferrule in each of its ends. Each cavity 153 is designed to receive and interlock with an optical plug 20 installed therein. When LC-type optical plugs are used, the cavity has a generally rectangular opening and includes a retaining feature on an internal wall of the cavity that interlocks with the latching tab 25 on the top side of optical plug 20.

[0027] Duplex connector 50 further includes guide members 51 and 52 on its top and bottom sides respectively, and each guide member includes a latch 55 that is designed to interlock with the particular cell 110 that ultimately receives the duplex connector.

[0028] FIG. 2 is a front side perspective view of a preferred embodiment of a connecting block 200. It is similar in all respects to the connecting block 100 shown in FIG. 1 with the exception that it includes twice as many cells 210 as are contained in connecting block 100. Nevertheless, since each cell is self contained and designed to receive a single duplex optical connector 50, the connecting block can be made arbitrarily large without substantial concern for overall dimensional tolerances, as would be the case if the connector held 12 optical plugs.

[0029] FIGS. 3 and 4 respectively show front and back views of a pair of adjacent cells 210-210 within connecting block 200. Cell 210, for example, is shaped to receive a duplex connector 50 (FIGS. 5-9) in its front side as shown in FIG. 3. Openings 213 and 214 are shaped to receive the tongue-like projections 51, 52 that are positioned on the top and bottom sides of the connector 50 in only one orientation. To accomplish this, opening 214 is made slightly wider than opening 213. Additionally, each opening 213, 214 contains a retaining feature (i.e., internal ledges 256-1 and 256-2) that is shaped to interlock with a mating feature 56 on the top and/or bottom sides of duplex connector 50 as shown in FIG. 9. Openings 211 and 212 are passages through the connecting block for enabling a pair of optical fibers to be interconnected. Each of the fibers is held within a separate optical plug, and the pair of optical plugs are inserted into opposite sides of the same opening (e.g., opening 211). The front side of each cell 210 is adapted to receive and interlock with a duplex optical connector 50, whereas the back side of each cell is adapted to receive and interlock with a pair of simplex optical plugs 20-3 and 20-4 as shown in FIG. 1. These simplex optical plugs 20-3 and 20-4 each include a latching tab 25 having shoulders 24 that interlock with retaining features (i.e., internal ledges 224-224) that are molded into the connecting block as best seen in FIG. 3. Opening 254 in the connecting block is created by the tool used for molding these internal ledges 224-224.

[0030] Duplex Optical Connector

[0031] FIG. 5 and FIG. 6 show perspective views of a duplex optical connector 50, which is designed to be easily and accurately installed into a mating receptacle. In particular, the duplex connector 50 is a unifying structure that functions to yoke a pair of simplex optical plugs 20-1, 20-2 (see FIG. 1) into a duplex configuration. Known duplex configurations are shown in U.S. Pat. No. 4,953,929; U.S. Pat. No. 5,123,071; U.S. Pat. No. 5,386,487; and U.S. Pat. No. 5,579,425. However, such configurations lack a number of advantages including dimensional stability, replacement ease of a simplex plug, and a common interlocking feature with a mating receptacle 110 (see FIG. 1).

[0032] Duplex connector 50 includes a pair of side-by-side optical ports that individually include a number of internal walls that define a cavity 153. Each cavity 153 has an opening in a back end of the duplex connector 50 that is shaped to receive a predetermined optical plug. In a preferred embodiment of the duplex connector, the opening is generally rectangular and the predetermined optical plug is an LC optical plug, which is disclosed in greater detail in U.S. Pat. No. 5,481,634 and U.S. Pat. No. 5,923,805. Nevertheless, it is understood that the cavities 153-153 within the duplex connector 50 could be shaped to receive other kinds of optical plugs, preferably those having low profiles.

[0033] Tongue-like projections 51, 52 are disposed on the top and bottom sides of the connector 50 and perform a number of valuable functions. The forward ends of the projections 51, 52 are tapered to facilitate insertion into a mating receptacle. Moreover, projection 52 is slightly wider than projection 51 to provide keying that prevents improper (upside down) insertion of the duplex connector into the receptacle. Finally, and perhaps most importantly, the tongue-like projections 51, 52 provide additional strength to withstand side-loading forces that would otherwise be transferred to brittle, ceramic alignment sleeves 60-60 (see FIG. 1) that may reside within bosses 58-58. Such side loading typically occurs when the duplex connector 50 is being removed from a mating receptacle.

[0034] Bosses 58-58 are tubular in construction and have an inside diameter of about 1.8 millimeters (mm). A bifurcation 59 is provided in one end of each boss that facilitates insertion of an alignment sleeve 60 (see FIG. 1), which functions to axially align the cylindrical ferrules that are associated with a pair or optical plugs (e.g., 20-1 and 20-3) that are to be interconnected. Alignment sleeves 60-60 may be made from metal, but are generally made from a ceramic material such as zirconia. They have a slightly smaller outside diameter than the inside diameter of the bosses and are able to float within the boss. A pair of cylindrical ferrules 21 (FIG. 1) having outer diameters of about 1.25 mm are inserted into opposite ends of the same alignment sleeve 60 during service. In this illustrative embodiment, a glass fiber (diameter about 125 microns) is held within a bore that extends along the central axis of each ferrule 21. In an alternate embodiment, the glass fiber and ferrule are replaced with a plastic fiber as shown in U.S. Pat. No. 5,923,805 whose outside diameter conforms to the inside diameter of the boss 58. It is noted that alignment sleeves are not necessary when plastic fiber is used. The dimensions provided in this paragraph are illustrative only, and are based on the preferred use of LC-type optical plugs.

[0035] Flexible latching members 55-55 are disposed on the top and bottom sides of the duplex connector 50, and each contains a wedge-shaped retaining feature 56 that is adapted to cooperate with corresponding mating feature within each cell 210 of a connecting block 200. More specifically, mating features 256-1 and 256-2 reside within openings 213, 214 of cell 210 as shown in FIG. 4. Illustratively, the duplex connector is molded from thermoplastic material such as polycarbonate.

[0036] FIG. 7 is a front-end view of the duplex optical connector 50 showing various details of its construction. Tubular bosses 58 project from the front wall 57 of the connector 50 and provide an opening 158 through which an optical fiber can pass and be connected, end to end, to another optical fiber. Guide members 51, 52 are the tongue-like projections that function to guide the duplex connector 50 into a cell of a connecting block 100, 200 or other receptacle. And while guide members 51, 52 are not required, they provide the valuable functions discussed above.

[0037] FIGS. 7 and 8 illustrate the various openings 153, 154, 158 into the connector 50 and their relative positioning in greater detail. Opening 153 in the back end of the connector 50 is shaped to receive and hold a simplex optical plug 20 in the manner disclosed in FIG. 9. A tool that is used during the molding process to form retaining features 54 within the connector that interlock with the optical plug creates opening 154. In particular, retaining feature 54 is designed to be intermatable with shoulders 24 on the latching tab 25 of an LC-type optical plug 20 (see FIG. 9). It is understood that different kinds of retaining features can be molded into the duplex connector 50 to accommodate different kinds of optical plugs. Finally, opening 158 extends completely through the connector, from its back side to its front side, to enable interconnection between optical fibers,

[0038] FIG. 9 is a partial cross-section view of the duplex optical connector of FIG. 8 having an optical plug 20 inserted therein. As illustrated, a ferrule 21 projects from the front end of the plug housing 22 and contains an optical fiber (not shown) that is disposed along its central axis. This ferrule 21 is held within a tubular alignment sleeve 60 that includes a slot along its length that allows its diameter to expand slightly and maintain a radial alignment force on each of the ferrules (only one is shown) that are inserted into the opposite ends of the sleeve 60. The sleeve has an outer diameter that is less than the inner diameter of the boss 58, and is free to move therein. A bifurcation 59 in the boss 58 is shown most clearly in FIG. 6 and enables the boss 58 to flex during insertion of the alignment sleeve 60 during manufacture. Such flexing is necessary because the end portions of the boss need to smaller than the alignment sleeve to keep it from becoming dislodged during service and handling. FIG. 9 illustrates the interaction between a shoulder 24 on the latching tab 25 of the optical plug and the retaining feature 54 within the duplex connector 50. This interaction holds the optical plug 20 within the duplex connector. The optical plug is released by simultaneously depressing the latching tab 25 and pulling the plug away from the connector 50.

[0039] In a similar manner, the duplex connector itself is held within another receptacle (e.g., cell 210 of connecting block 200 shown in FIGS. 3 and 4). The flexible latching members 55-55 on the top and bottom sides of the duplex connector 50 function in the same manner as the latching tab 25 on the optical plug 20; and the wedge-shaped retaining features 56-56 function in the same manner as the shoulder 24 on the optical plug. The duplex connector 50 is released from the cell 210 by simultaneously depressing both latching members 55-55 and pulling the duplex connector away from the cell. For completeness, the optical plug 20 is shown terminating an optical cable 30 with a bend-limiting boot 40 disposed at the junction between the cable 30 and the optical plug 20. The boot 40 is made from an elastomeric material, and it functions to preclude severe bending of the optical fiber, which would increase the transmission loss of the optical fiber.

[0040] Although various particular embodiments of the present invention have been shown and described, modifications are possible within the scope of the invention. These modifications include, but are not limited to the use of: different materials in the construction of the connecting block and duplex connector; different kinds of optical plugs having different latching features; and the use of optical cables and plugs that are designed to accommodate plastic optical fiber.