Abstract:
An adapter includes a mechanical frame, which is configured to be inserted into a SFP-type receptacle and contains a socket for receiving a plug of a twisted-pair-type cable. First electrical terminals, held by the mechanical frame, are configured to mate with a connector in the receptacle. Second electrical terminals, held within the socket, are configured to mate with electrical connections of the plug. Circuitry connects the first and second electrical terminals so as to enable interoperation of the plug with the receptacle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application 61/383,343, filed Sep. 16, 2010, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to data communications, and specifically to adapters for bridging between connectors of different types. 
     BACKGROUND 
     Small Form-factor Pluggable (SFP) modules are used in various telecommunication and data networking applications to interface between a printed circuit board in a network device and a network cable (which may be electrical or fiberoptic). Typically, the SFP receptacle is mounted on the printed circuit board with appropriate electrical connections to the circuit traces on the board, and a connector at the end of the cable plugs into the receptacle. The connector itself commonly contains signal conversion circuitry and is therefore referred to as a “transceiver.” 
     The mechanical and electrical characteristics of various SFP modules have been defined by industry organizations. For example, the SFP+ specification defines hot-pluggable modules that may be used at data rates up to 10 Gb/s. Details of these modules have been set forth by the SFF Committee in the  SFF -8431  Specifications for Enhanced Small Form Factor Pluggable Module SFP + (Revision 4.1, Jul. 6, 2009), which is incorporated herein by reference. This specification, as well as other SFP specifications, is available at ftp.seagate.com/sff. 
     Quad Small Form-factor Pluggable (QSFP) modules are used in similar applications to the SFP modules described above and support four parallel communication channels at 10 Gb/s. The mechanical and electrical characteristics of QSFP modules are described in the  SFF -8436  Specification for QSFP+ Copper and Optical Modules  (Revision 3.4, November, 2009), which is also incorporated herein by reference. 
     U.S. Pat. No. 7,335,033, whose disclosure is incorporated herein by reference, describes a form factor converter configured to concurrently connect to a circuit board module and a small form factor transceiver. The form factor converter includes an exterior portion defining a large form factor to fit within the device mounting section of the circuit board module, and an interior portion defining a small form factor location to receive at least a portion of a small form factor transceiver. 
     U.S. Pat. No. 7,934,959, whose disclosure is incorporated herein by reference, describes an adapter, which includes a mechanical frame, which is configured to be inserted into a four-channel SFP receptacle and to receive inside the frame a single-channel SFP cable connector. First electrical terminals, held by the mechanical frame, are configured to mate with respective first pins of the receptacle. Second electrical terminals, held within the mechanical frame, are configured to mate with respective second pins of the connector. Circuitry couples the first and second electrical terminals so as to enable communication between the connector and one channel of the receptacle while terminating the remaining channels of the receptacle. 
     10 GBASE-T Ethernet is a standard defined by IEEE 802.3an-2006, which is incorporated herein by reference. This standard provides connections at 10 Gb/s over unshielded or shielded twisted pair cables, over distances up to 100 meters. 10 GBASE-T can use the same cable infrastructure as legacy standards, such as 1000BASE-T, including Category 6 (or better) cabling and RJ45 connectors. It thus allows a gradual upgrade from 1000BASE-T using autonegotiation to select which speed to use. The features of 10 GBASE-T are described in detail by Barrass, et al., in a white paper entitled, “10 GBASE-T: 10 Gigabit Ethernet over Twisted-pair Copper,” published by the Ethernet Alliance (Austin, Tex., Version 1.0, August, 2007), which is available at www.teranetics.com/pdf/EA — 10GBase-T-Overview.pdf and is incorporated herein by reference. 
     SUMMARY 
     Embodiments of the present invention that are described hereinbelow provide adapters and methods for interworking of connectors and cables defined by different protocols and specifications. 
     There is therefore provided, in accordance with an embodiment of the present invention, an adapter, including a mechanical frame, which is configured to be inserted into a SFP-type receptacle and contains a socket for receiving a plug of a twisted-pair-type cable. First electrical terminals are held by the mechanical frame and configured to mate with a connector in the receptacle. Second electrical terminals are held within the socket and configured to mate with electrical connections of the plug. Circuitry connects the first and second electrical terminals so as to enable interoperation of the plug with the receptacle. 
     In a disclosed embodiment, the plug is a RJ45 plug, and the SFP-type receptacle is selected from a group of receptacles consisting of QSFP, QSFP+ and SFP+ receptacles. 
     In some embodiments, the connector in the receptacle is an edge connector, and the circuitry includes a printed circuit board, and the first electrical terminals are located at an end of the printed circuit board and are configured to mate with the edge connector. 
     Typically, the circuitry includes at least one integrated circuit. In a disclosed embodiment, the at least one integrated circuit is configured to convert between a single-lane signal on the first electrical terminals and a multi-lane signal on the second electrical terminals. 
     Additionally or alternatively, the circuitry may be configured to convert between a 10 GBASE-R interface of the receptacle and a 10 GBASE-T interface of the plug. 
     There is also provided, in accordance with an embodiment of the present invention, a method for communication, which includes inserting an adapter into a SFP-type receptacle. The adapter includes a mechanical frame, first and second electrical terminals, and circuitry enabling interoperation of the plug with the receptacle, as described above. The plug of the twisted-pair-type cable is inserted into the socket. 
     The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, pictorial illustration showing connection of an Ethernet cable to a SFP+ receptacle via an adapter, in accordance with an embodiment of the present invention; 
         FIGS. 2A and 2B  are schematic, pictorial views of the adapter of  FIG. 1 , seen from two different angles; 
         FIG. 3  is a block diagram that schematically shows electrical components of an SFP+-RJ45 adapter, in accordance with an embodiment of the present invention; 
         FIGS. 4A and 4B  are schematic, pictorial views of a QSFP-RJ45 adapter, seen from two different angles, in accordance with another embodiment of the present invention; and 
         FIG. 5  is a block diagram that schematically shows electrical components of an QSFP-RJ45 adapter, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Many types of high-speed network equipment, such as switches and advanced network interface cards, have SFP receptacles for connection of cables to other equipment. It would be desirable to enable such equipment to accept RJ45 connectors, as well, and thereby be able to communicate over standard twisted pair cables directly with 10GBASE-T equipment. Embodiments of the present invention therefore provide adapters that fit inside an SFP receptacle (such as QSFP, QSFP+ or SFP+) and accommodate a RJ45 plug, both mechanically and electrically, thus enabling cables that are terminated with RJ45 plugs to be plugged into SFP receptacles. 
     Although the embodiments that are described hereinbelow relate specifically to interworking of SFP+ with QSFP with RJ45 plugs, the principles of the present invention may similarly be applied in mating other heterogeneous types of plugs and receptacles. 
     Reference is now made to  FIGS. 1 ,  2 A and  2 B, which schematically illustrate a SFP+-RJ45 adapter  20 , in accordance with an embodiment of the present invention.  FIG. 1  shows how adapter  20  is used in connecting an Ethernet cable  38 , such as a Category 6 cable, to a piece of network equipment  22 .  FIGS. 2A and 2B  show details of adapter  20  from two different angles. 
     Adapter  20  is plugged into a SFP+ receptacle  26  in a panel  24  of equipment  22 . (Typically, panel  24  contains multiple receptacles with respective indicator lamps and other controls, as are known in the art, but only a single receptacle is shown here for the sake of simplicity). Receptacle  26  could simply receive a cable with a SFP+ plug (not shown). In some cases, however, it may be desired to couple equipment  22  to legacy equipment that contains only RJ45 sockets, for example, or it may be desired to use legacy twisted-pair cables instead of more costly twin-ax copper or fiberoptic cables that are commonly used with SFP+ transceivers. For these sorts of cases, adapter  20  permits cable  38  with a RJ45 connector  36  to mate with receptacle  26 . A release mechanism, such as a pull tab  42  or a lever, can be used to remove the adapter from the receptacle when it is no longer needed. 
     Receptacle  26  comprises a cage, which is mounted on a printed circuit board  28  behind panel  24 . Adapter  20  comprises a mechanical frame  40  having outer dimensions that are similar or identical to those of a standard SFP+ connector and thus fits into the cage. Outer electrical terminals  30  on adapter  20  mate with an edge connector  32  in receptacle  26  in the same manner as would the terminals of a SFP+ connector. Terminals  30  are located at the end of a miniature printed circuit board  46  inside frame  40 . A collar  44  holds adapter  20  in place and provides a continuous ground connection to frame  40  when the adapter is inserted into receptacle  26 . 
     At the outer end of adapter  20 , opposite terminals  30 , the adapter comprises a socket  34  which has inner dimensions and internal connections that are identical to those of a RJ45 socket and can thus receive RJ45 plug  36 . The connections in socket  34  connect to circuit board  46 . Circuits on board  46  convert 10 Gigabit Ethernet from the GBASE-R PCS (physical coding sublayer) and PMA (physical medium attachment) components of the physical layer interface (PHY) that are provided by receptacle  26  to the 10 GBASE-T PCS, PMA, and PMD (physical medium dependent) PHY components accepted by plug  36 , and vice versa. 
       FIG. 3  is a block diagram that schematically shows electrical components of SFP+-RJ45 adapter  20 , in accordance with an embodiment of the present invention. The adapter includes an integrated circuit (IC)  48  (or a number of such circuits), connected between SFP+ terminals  30  and RJ45 terminals  52  in socket  34 . Circuit  48  converts between the single-lane 10 GBASE-R PHY that is provided to receptacle  26  at edge connector  32  and the four-lane 10 GBASE-T PHY that is used on cable  38 . The conversion includes the PMD, PMA and PCS components of the Ethernet PHY. ICs capable of performing this sort of conversion are commercially available and include, for example, the AQ1103 PHY Transceiver produced by Aquantia (Milpitas, Calif.), as well as similar products offered by Solarflare Communications (Irvine, Calif.) and Teranetics (San Jose, Calif.). Electrical power at the voltage levels required by circuit  48  is provided by a power conversion circuit  50 , including one or more DC/DC converters and regulators. 
     Thus, adapter  20  appears to equipment  22  to be a standard SFP+ transceiver, which accepts and outputs signals on terminals  30  that are compatible with a standard 10 GBASE-R PHY. At the same time, the adapter appears to cable  38  to be a standard 10 GBASE-T interface, with a 10 GBASE-T PHY and socket  34 . In this manner, adapter  20  permits interworking of the SFP+ receptacle with the RJ45 plug. 
     Reference is now made to  FIGS. 4A and 4B , which schematically show two different schematic, pictorial views of a QSFP-RJ45 adapter  60 , in accordance with another embodiment of the present invention. The features of adapter  60  are similar to those of adapter  20  described above, including terminals  62 , a pull-lever  64 , and socket  34 , but are dimensioned for insertion into a slightly larger QSFP receptacle (not shown), with a 4×10 Gb/s interface and different pin definitions. 
       FIG. 5  is a block diagram that schematically shows electrical components of QSFP-RJ45 adapter  60 , in accordance with an embodiment of the present invention. As in the preceding embodiment, adapter  60  comprises at least one integrated circuit  68 , which is mounted on a miniature printed circuit board  66  and is connected between QSFP terminals  62  and RJ45 terminals  52  in socket  34 . Circuit  68  typically converts between single-lane 10 GBASE-R or 10 GBASE-X PHY signals on terminals  62  and the four-lane 10 GBASE-T signals on terminals  52 . 
     Alternatively, adapter  60  may be configured to handle 40 Gigabit Ethernet signals, and thus convert between 40 GBASE-R and 40 GBASE-T formats (with a suitable connector and cable to handle the 40 Gb/s data rate). In this case, the PHY IC on the adapter is configured for 40 Gb/s operation and has four lanes on both the 40 GBASE-R side and the 40 GBASE-T side. 
     Although the above figures show particular implementations of the mechanical and electrical connections used in adapters  20  and  60 , variations on these implementations will be apparent to those skilled in the art, after reading the above disclosure. Such variations are considered to be within the scope of the present invention. More generally, the principles of the present invention may similarly be applied in adapting other SFP-type receptacles to mate with standard network cable plugs. 
     It will thus be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.