Abstract:
A fiber optic communications cable for providing a short range, high speed data communications link between information system units, including an optical fiber with an integral housing at each end having an electrical connector extending from the housing and adapted to mate with a corresponding electrical connector on an external information system unit for transferring an information signal between the cable and the unit. A signal converter in the integral housing&#39;s converts the information signal between an electrical signal and a corresponding optical signal.

Description:
[0001]     The present application is related to U.S. application Ser. No. 10/612,886 filed on Jul. 3, 2003, entitled “Modular Media Converter”, the contents of which are incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to high speed data communications cables, and more particularly to optical fiber cables and electro-optical signal converters used for short-range coupling of information system units.  
       BACKGROUND OF THE INVENTION  
       [0003]     High speed data communications networks utilize optical fiber cables for data transmission between information system units such as computers, mass data storage devices, and routers. Such units typically employ electrical connectors which couple to electrical connectors associated with electrical cables. To couple such units to an optical fiber cable, an electro-optical converter or transceiver is employed which interfaces between the electrical connector and the optical fiber cable.  
         [0004]     Examples of electrical connectors know in the prior art communications applications are illustrated in  FIGS. 1A and 1B . More particularly,  FIG. 1A  shows an electrical connector  10  designed for use in a 4-channel InfiniBand™ electrical interconnect.  FIG. 1B  shows an electrical connector plug  12  designed for use in a 12-channel InfiniBand™ electrical interconnect. Electrical connectors  10  and  12  are inserted in associated electrical receptacles mounted on an information systems unit to establish electrical contact with the input/output terminals of such unit  
         [0005]      FIGS. 2A and 2B  respectively show an optical cable connector  14  and an optical cable connector receptacle  16  used in InfiniBand™ 4-channel and 12-channel optical interconnects. The optical connector  14  is adapted to mate with optical connector receptacle  16  to enable the four independent optical signals traveling through four fibers in the attached optical cable  18  to communicate with corresponding receivers disposed in the optical connector receptacle  16 . The committee setting standards for both 10 Giga-bit Fiber Channel (10 GFC) and 10 Giga-bit Ethernet (10 GbE) is considering to use the above described electrical and optical connector plugs/receptacles in systems complying with these standards.  
         [0006]      FIG. 3  shows a conventional InfiniBand™ interface card  20  that is adapted to be inserted in system  22 . Depending on the function it is adapted to perform, the InfiniBand™ interface card  20  is commonly referred to as a Host-Channel Adapter (HCA) or a Target Channel Adapter (TCA). Each InfiniBand™ interface card  20  includes one or more printed circuit boards (PCB) that are alternatively referred to hereinbelow as host broads. Each such PCB typically includes hardware adapted to establish communication with other PCBs, with other interface cards or modules via a multitude of electrical wires or optical cables.  
         [0007]      FIG. 4A  shows an electrical connector receptacle  24  mounted on a host board  26  of a TCA/HCA card. Electrical connector receptacle  24  is adapted so as to mate with electrical connector plug  10  (also see  FIG. 1A ).  FIG. 4B  shows an optical connector receptacle  28  mounted on a host board  30  of a TCA/HCA card. Optical connector receptacle  28  is adapted so as to mate with optical connector plug  14  (also see  FIG. 2A ).  
         [0008]     In conventional systems, the host board is often adapted to mate with either an electrical connector plug or an optical connector plug. If the host board is adapted to mate with an electrical connector plug and a subsequent need arises to carry the signals over distances longer than those for which electrical wires, i.e., copper may be used (InfiniBand™ specification calls for copper wire to be used for distances up to 17 meters), the user may need to replace the TCA/HCA card with a card adapted to receive an optical cable so as to be able to handle optical signals, thereby increasing cost. Similarly, if the host board card is adapted to mate with an optical connector plug, and a subsequent need arises to carry the signals over a relatively shorter distances, it may be more cost effective to replace the TCA/HCA card with a card adapted to receive a copper wire so as to be able to handle electrical signals.  
         [0009]     Accordingly, media adapters have been developed to enable optical signals carried via an optical cable to be coupled to electrical receptacles. Such media adapters include a fiber optic cable with an electrical plug coupled to on one end and an optical plug coupled to another end. The electrical plug is adapted to mate with an electrical connector receptacle on a host board and the optical plug is adapted to mate with an optical connector receptacle. The electrical signals present on the electrical receptacle are converted to optical signals by a transceiver disposed in the media adapter and carried over fiber optic cable. Conventional media adapters are connectorized and are thus relatively expensive. Furthermore, safety issues remain a concern if a user detaches the optical cable from the coupling plugs and looks at the light beams emanating from the lasers disposed therein.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     Briefly, and in general terms, the present invention provides a communications cable for providing a short range, high speed data communications link between information system units including an optical fiber with an integral housing at each end having an electrical connector extending from the housing and adapted to mate with a corresponding electrical connector on an external information system unit for transferring an information signal between the cable and the unit; and a signal converter in the integral housing connected to the electrical connector for converting an information signal between an electrical signal and a corresponding optical signal. In accordance with one embodiment of the present invention, a cable assembly includes a fiber optic cable with a pair of optical connector plugs coupled to each one of its ends. The optical connector plugs are adapted to mate with two electrical connector receptacles already present on two host boards. The cable assembly thus enables communication between the electrical receptacles of the two host boards to be carried out via optical signals. In other words, the cable assembly is adapted to receive electrical signals from a first electrical receptacle—mounted on the first host board—via one of its optical connector plugs, and subsequently convert the received electrical signals to optical signals and deliver the optical signals via the fiber optic cable to the other optical connector plug. The receiving optical connector plug converts the optical signals to electrical signals and delivers the converted electrical signal to the second electrical connector receptacle mounted on the second host board.  
         [0011]     The electrical connector receptacle has physical and electrical characteristics defined by the same standard as that defining the physical and electrical characteristic of the optical plugs. Accordingly, the same electrical receptacle on the host board may be used to receive both an electrical connector plug or the optical connector plug of the cable assembly. Accordingly, if the distance between the two electrical connector receptacles (i.e., the two host boards) is, e.g., more than 15 meters, a cable assembly, in accordance with the present invention, may be used to establish communication between the two host boards. If, on the other hand, the distance between the two host boards is, e.g., less than 15 meters, a conventional copper cable with standard electrical connector plugs may be used to establish communication between the two host boards.  
         [0012]     Each optical plug includes, in part, an optical engine mounted on a board, a top housing shell, and a bottom housing shell. In some embodiments, the fiber optic cable is attached to the optical plugs via a strain relief boot. Because the fiber optic cable is attached to the optical plugs and may not be easily removed, the user is not exposed to safety hazards that may result from viewing the laser beams. In other embodiments, the fiber optic cable is glued to the optical plugs.  
         [0013]     In accordance with another embodiment of the present invention, a cable assembly includes, in part, a connector plug from which a fiber optic cable and an electrical cable are fanned out. The connector plug receives and processes (e.g., amplify, filter, etc.) electrical signals from an electrical connector receptacle mounted on a host board. The processed signals that are to be transmitted via the fiber optic cable are converted to optical signals using an optical engine. The processed signals that are to be transmitted via the electrical cable may be further processed before being transmitted. In some embodiments, the signals transmitted by the fiber optic cable may be the same as those transmitted by the electrical cable and may include the entire set of the signals received from the connector receptacle. In yet other embodiments, the signals transmitted by the fiber optic cable may be different from those transmitted by the electrical cable.  
         [0014]     In some embodiments of the present invention, the optical engines as well as the integrated circuits are powered by circuitry disposed on the host boards via the same supply voltages which power the components on the host boards. One or more of the connectors of the electrical receptacles are configured to deliver the supply voltages to the optical engines as well as the integrated circuits mounted on one or more boards disposed within the connector plug and configured to process the received electrical signals.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1A  shows an electrical connector plug adapted for use in a 4-channel InfiniBand™ electrical interconnects, as known in the prior art.  
         [0016]      FIG. 1B  shows an electrical connector plug adapted for use in a 12-channel InfiniBand™ electrical interconnects, as known in the prior art.  
         [0017]      FIG. 2A  shows an optical connector plug used in InfiniBand™ interconnects, as known in the prior art.  
         [0018]      FIG. 2B  shows an optical connector receptacle used in InfiniBand™ interconnects, as known in the prior art.  
         [0019]      FIG. 3  shows a conventional InfiniBand™ interface card.  
         [0020]      FIG. 4A  shows an electrical connector receptacle mounted on a host board, and an electrical connector plug adapted to mate therewith.  
         [0021]      FIG. 4B  shows an optical connector receptacle mounted on a host board, and an optical connector plug adapted to mate therewith.  
         [0022]      FIG. 5  shows a cable assembly, in accordance with a first embodiment of the present invention.  
         [0023]      FIG. 6  shows the cable assembly of  FIG. 5  positioned to establish communications between a pair of electrical connector receptacles mounted on two different host boards.  
         [0024]      FIG. 7  is an exploded view of one exemplary embodiment of the optical connector plug of the cable assembly of  FIG. 5 .  
         [0025]      FIG. 8  is an exploded view of another exemplary embodiment of the optical connector plug of the cable assembly of  FIG. 5 .  
         [0026]      FIG. 9  shows a cable assembly having a connector plug from which a fiber optic cable and an electrical cable are fanned out, in accordance with a second embodiment of the present invention.  
         [0027]      FIG. 10  is an exploded view of one exemplary embodiment of the connector plug of  FIG. 9  from which the fiber optic cable and electrical cable are fanned.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     In accordance with one embodiment of the present invention, a cable assembly includes a fiber optic cable with a pair of optical connector plugs coupled to each one of its ends. The optical connector plugs are adapted to mate with two electrical connector receptacles already present on two host boards. The cable assembly thus enables communication between the electrical receptacles of the two host boards to be carried out via optical signals. In other words, the cable assembly is adapted to receive electrical signals from a first electrical receptacle—mounted on the first host board—via one of its optical connector plugs, and subsequently convert the received electrical signals to optical signals and deliver the optical signals via the fiber optic cable to the other optical connector plug. The receiving connector plug converts the optical signals to electrical signals and delivers the converted electrical signal to the second electrical connector receptacle mounted on the second host board.  
         [0029]     The electrical connector receptacle has physical and electrical characteristics defined by the same standard as that defining the physical and electrical characteristic of the optical plugs. Accordingly, the same electrical receptacle on the host board may be used to receive both an electrical connector plug or the optical connector plug of the cable assembly. Accordingly, if the distance between the two electrical connector receptacles (i.e., the two host boards) is, e.g., more than 15 meters, a cable assembly, in accordance with the present invention, may be used to establish communication between the two host boards. If, on the other hand, the distance between the two host boards is, e.g., less than 15 meters, a conventional copper cable with standard electrical connector plugs may be used to establish communication between the two host boards.  
         [0030]      FIG. 5  shows a cable assembly  100 , in accordance with one embodiment of the present invention. Cable assembly  100  includes, in part, a fiber optic cable  110 , a first optical connector plug  105  coupled to a first end of fiber optic cable  110 , and a second optical connector plug  115  coupled to a second end of fiber optic cable  110 . Each of the optical connector plugs (hereinafter alternatively referred to as optical plug)  105 , and  115 , is adapted to mate with a different electrical connector receptacle mounted on a host board, such as electrical receptacle  104  of host board  106 , shown in  FIG. 6 .  
         [0031]     In  FIG. 6  cable assembly  100  is shown as being in alignment with electrical receptacle  104 —mounted on host board  106 —and electrical receptacle  108  that is mounted on electrical host board  110 . If the distance d between host board  106  and  110  is less than the maximum recommended distance for which copper cable is adapted to be used, a copper cable (not shown), such as Category 5 cable, may be used to connect electrical receptacle  104  with electrical receptacle  108  in order to establish communication between these two electrical receptacles. If, on the other hand, distance d between host board  106  and  110  is greater than the maximum recommended distance for which copper cable is adapted to be used, connector plug  105  is mated directly with electrical receptacle  104  and connector plug  115  is mated directly with electrical receptacle  108  in order to establish communication between these two electrical receptacles.  
         [0032]     Disposed within each plug  105  and  115  of cable assembly  100  is an electrical/optical engine (hereinafter alternatively referred to as optical engine) adapted to convert electrical signals to optical signals and vice versa. As known to those skilled in the art, each optical engine includes components such as, lasers, lenses, laser drivers, etc. The optical engine in each optical plug, e.g. optical plug  105 , is adapted to receive electrical signals from its mating electrical receptacle, e.g., electrical receptacle  104 , convert that electrical signal to optical signal, and thereafter deliver that optical signal via fiber optic cable  110  to the other optical plug, e.g., optical plug  115 . The optical plug  115  receiving the optical signal converts the received optical signal to electrical signal and delivers the converted electrical signal to, e.g., electrical receptacle  108 .  
         [0033]      FIG. 7  is an exploded view of one exemplary embodiment  150  of each of optical plugs  105 ,  110 . Optical plug  150  is shown as including, in part, an optical engine  180  mounted on board  152 , top housing shell  160 , bottom housing shell  166  sleeve  170 , and strain relief boot  172 . The optical engine  150  is mounted and secured to board  152 . Thereafter, the board  152  is disposed between top and bottom housing members  160  and  166 . It is understood that board  152  may be a flexible circuit board or a rigid circuit board. In the embodiment  150 , the optical engine  180  is an optical transceiver, however, in other embodiments, the optical engine  180  may be an optical transmitter or an optical receiver. A train relief boot  172  is adapted to prevent fiber optic cable  110  from being detached from optical plug  150 . Since fiber optic cable  110  is attached to optical plug  150  and may not be easily removed, the user is not exposed to safety hazards that may result from viewing the laser beams present therein.  
         [0034]     Optical plug  150  complies with the same industry standard with which host board  106  and electrical receptacle  104  also comply. For example, if host board  106  and electrical receptacle  104  are formed in accordance with InfiniBand™ specifications, optical plug  150  is also compliant with InfiniBand™ specifications. If host board  106  and electrical receptacle  104  are formed so as to comply with Host-Channel Adapter (HCA) or a Target Channel Adapter (TCA) specifications and standards, optical plug  150  is also compliant with these specifications and standards. Therefore, board  152  is formed so as to receive any standard compliant optical engine.  
         [0035]      FIG. 8  is an exploded view of another exemplary embodiment  190  of each of optical plugs  105 ,  110 . Optical plug  190  is shown as including, in part, an optical engine  180  mounted on board  152 , top housing shell  160 , bottom housing shell  166 , and sleeve  170 . In accordance with this embodiment, fiber optic cable  110  is affixed to optical plug  190  via glue  191 , or other adhesive, so as not to be easily removed. The user is therefore not exposed to safety hazards that may result from viewing the laser beams. The glue used in accordance with this embodiment, is adapted to maintain its properties under a wide range of temperatures and is available from a number of vendors, such as 3M Co, located at 3M Center, St. Paul, Minn., 55144, USA.  
         [0036]     As described above, cable assembly  100  dispenses the need for replacing electrical receptacle  104  or host board  106  in the field if a decision is made to use an optical fiber in place of copper wires as the transmission medium. As described above, optical engine  180  may be supplied or manufactured by any commercial vendor or manufacturer so long as it complies with the same standard as that with which host board  106  or electrical receptacle  104  are also adapted to comply.  
         [0037]     Because fiber optic cable  110  is not connectorized (i.e., fiber optic cable  110  may not be detached from the optical plugs) it provides a relatively high level of eye safety. Furthermore, because fiber optic cable  110  is not connectorized, it has improved matched ends properties, as described further below. In a conventional connectorized optical cable, a first optical engine coupled to a first end of the optical cable is required to operate with any optical engine coupled to the other end of the optical cable, notwithstanding their respective manufactures. Therefore, the first optical engine is required to function over a wide range of operating conditions, resulting in yield loss and a relatively more extensive testing. In contrast, because the two optical engines disposed at the two ends of cable assembly  100 , are only required to operate with each other, they are easier two match; in other words, cable assembly  100  has matched ends. Moreover, in accordance with the present invention, because the two optical engines are matched, a higher manufacturing yield is achieved and less extensive testing of the optical engines are required.  
         [0038]     In the embodiment shown in  FIGS. 7-8 , optical engine  180  is mounted to board  152  via a fastener, such as a screw or bolt. In other embodiments, optical engine  180  may be, for example, soldered to board  152 . In some embodiment, optical engine  180  may have four-channels. In yet other embodiments, optical engine  180  may have, e.g., twelve channels.  
         [0039]      FIG. 9  shows a cable assembly  300  in accordance with another embodiment of the present invention. Cable assembly  300  includes, in part, one or more fiber optic cables  305  adapted to carry optical signals, one or more electrical cables (e.g., copper wire)  310  adapted to carry electrical signals  310 , first connector plug  315  coupled to a first end of fiber optic cable  305  and electrical cable  310 , a second optical connector plug  115  coupled to a second end of fiber optic cable  305 , and a third electrical connector plug  325  coupled to a second end of electrical cable  310 .  
         [0040]     Connector plug  315  is adapted to mate with an electrical connector receptacle mounted on a host board, such as electrical receptacle  104  of host board  106 , shown in  FIG. 6 . Connector plug  315  is also adapted to receive and process (e.g., amplify, filter, etc.) electrical signals and deliver a subset or the whole set of the processed electrical signals to electrical cable  310 . Connector plug  315  is further adapted to deliver a subset or the whole set of the processed electrical signals to fiber optic cable  305 , as described further below.  
         [0041]      FIG. 10  is an exploded view of one exemplary embodiment of connector plug  315 . Connector plug  315  is shown as including, a board  320  which may be a flexible board or a rigid board, an electrical connector array  340 , integrated circuits  325  and  330  and optical engine  335  mounted on board  320 , top housing shell  360 , bottom housing shell  365 , and strain relief boot  375 . In the embodiment shown in  FIG. 10 , integrated circuit  330  as well as optical engine  335  are mounted on a front side of board  320  which is different from the side on which integrated circuit  325  is mounted. It is understood that in other embodiments, the positions on which these components are mounted may be different from those shown in  FIG. 10 . As seen from  FIG. 10 , board  152  is disposed between top and bottom housing shells  360  and  365 .  
         [0042]     Integrated circuit  325  processes the electrical signals it receives from connector array  340  and delivers the processed signals to one or both of integrated circuit  330  and optical engine  335 . In some embodiments, the processing functions performed by integrated circuit  325  may include, for example, amplification, filtering, etc. In some embodiments, optical engine  335  is an optical transceiver, however, in other embodiments, optical engine  335  may be an optical transmitter or an optical receiver.  
         [0043]     Integrated circuit  325  is adapted so as to process the electrical signals it receives from connector array  340  to determine whether these signals are to be delivered to electrical cable  310  or to fiber optic cable  305  or both. Integrated circuit  325  delivers the signals that are to be carried by electrical cable  310  to integrated circuit  330 . Similarly, integrated circuit  325  delivers the signals that are to be carried by fiber optic cable  310  to optical engine  335 . Integrated circuit  330  may perform additional processing of the signals it receives (e.g., amplify) before delivering these signals to the electrical wires disposed in electrical cable  310 . In some embodiment, integrated circuit  325  delivers the processed electrical signals to electrical cable  310  without sending these signals to integrated circuit  330 . Optical engine  335  converts the electrical signals it receives from integrated circuit  325  to optical signals and delivers the optical signals to fiber optic cable  305 .  
         [0044]     Accordingly, electrical cable  310  and fiber optic cable  305  may respectively carry electrical and optical signal concurrently. Furthermore, if the distance between the two electrical connector receptacles (i.e., the two host boards) is, e.g., more than 15 meters, the signals are carried by fiber optic cable  305 , in accordance with the present invention, to establish communication between the two host boards. If, on the other hand, the distance between the two host boards is, e.g., less than 15 meters, the signals are carried by electrical cable  310 , e.g., conventional copper cable, to establish communication between the two host boards. In some embodiments, fiber optic cable  305  and electrical cable  310  may carry the same information. In yet other embodiments, fiber optic cable  305  and electrical cable  310  may carry different information. Integrated circuits  325  and  335  as well as optical engine  335  may be powered by the media detection circuitry.  
         [0045]     Strain relief boot  172  is adapted to prevent fiber optic cable  110  from being detached from optical plug  150 . Because fiber optic cable  110  is attached to optical plug  150  and may not be easily removed, the user is not exposed to safety hazards that may result from viewing the laser beams present therein.  
         [0046]     It is understood that the above embodiments of the present invention are illustrative and not limitative. For example, the invention in not limited by the type of optical engine disposed in the optical plug of each end of the assembly cable. The invention is not limited by the type of circuit board, flexible or rigid, on which the optical engine is mounted. The invention is not limited by the number of channels, speed or specific electrical or optical configuration that, e.g., the optical engine is adapted to handle. Other variations, modifications, additions, deletions are obvious in light of the above disclosure and are intended to fall within the scope of the appended claims.