Abstract:
Embodiments of the present invention relate to the field of fiber optic connectivity, and more specifically, to systems and methods for connecting fiber optic transceivers. In an embodiment, the present invention provides a system which enables the interconnection of fiber optic transceivers such as, for example, 24-fiber transceivers like the 100GBASE-SR10 transceivers while maintaining appropriate fiber polarity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/057,357 filed on Sep. 30, 2014, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     Embodiments of the present invention relate to the field of fiber optic connectivity, and more specifically, to systems and methods for connecting fiber optic transceivers. 
     BACKGROUND 
     Fiber optic communication generally takes place over a network where optical signals travel within an optical waveguide (e.g., an optical fiber) between an optical transmitter (e.g., LEDs or VCSELs [vertical-cavity surface-emitting lasers]) and an optical receiver (e.g., optoelectronic sensors). To achieve proper operation, it is especially important to ensure that an optical fiber that is coupled to a transmitter at one end is also coupled to a receiver on another end. This configuration is critical because each fiber channel needs to have a means for generating a signal and a means for sensing a signal. 
     A variety of different transceivers are in existence today. The arrangement of the transmit lanes (Tx) and receive lanes (Rx) of those transceivers are typically governed by various standards. For example, IEEE 802.3ba, which is incorporated herein by reference in its entirety, provides the basis for the positioning of Tx and Rx lanes in a 100GBASE-SR10 transceiver. Per IEEE 802.3ba, a 100GBASE-SR10 transceiver employs two rows of 12 fibers each, with 10 of the 12 top center lanes acting as the Rx lanes and 10 of the 12 bottom center lanes acting as the Tx lanes. The top/bottom orientation is determined with reference to a receptacle key being positioned on top when looking into the receptacle. Although there are no particular lane assignments among the Tx or Rx lanes, and thus no corresponding Tx/Rx pairs, it is still imperative that a fiber coupled to a Tx lane on one transceiver be routed to an Rx lane on another transceiver. 
     While theoretically a pair of 100GBASE-SR10 transceivers may be interconnected via a 24-fiber trunk cable, practical implementation of such a network may pose a number of problems which are linked to the existing fiber optic infrastructure. Many environments where fiber optic connectivity is in use today, such as for example data centers, employ 12-fiber backbone/trunk cables/links. These cables are often hidden from view and are not easily accessible. As a result, upgrading the existing backbone infrastructure can become costly and disruptive. 
     Options for routing signals of a 24-fiber transceiver through multiple trunk cables have been discussed in various standards, including TIA-568-C.0-2 which is incorporated herein by reference in its entirety. However, these implementations still have certain shortcomings. For example, the Method A described in TIA-568-C.0-2 relies on using two different harnesses. While Method B described in TIA-568-C.0-2 eliminates the need for different harnesses, it requires a key-up to key-up mating scheme between the harnesses and the trunk cables. In both cases, these drawbacks can create installation problems and/or obstacles. 
     As a result, there is a continued need for improved systems and methods which enable the interconnection of fiber optic transceivers, and in particular, 24-fiber transceivers such as the 100GBASE-SR10 transceivers. 
     SUMMARY 
     Accordingly, at least some embodiments of the present invention provide systems and methods which enable the interconnection of fiber optic transceivers such as, for example, 24-fiber transceivers like the 100GBASE-SR10 transceivers. 
     In an embodiment, the present invention is a communication link for use in a fiber optic communication network. The communication link includes a first breakout harness and a second breakout harness, where each of the first breakout harness and the second breakout harness includes: an equipment-side connector including a key, and a first and a second row of optical fiber channels positioned relative to the equipment-side connector key; a first trunk-side connector including a key and a row of optical fiber channels positioned relative to the first trunk-side connector key; a second trunk-side connector including a key and a row of optical fiber channels positioned relative to the second trunk-side connector key; a first plurality of optical fibers connecting the first row of optical fiber channels of the equipment-side connector to the row of optical fiber channels of the first trunk-side connector such that a left-to-right order of each of the first plurality of optical fibers is the same in both of the equipment-side connector and the first trunk-side connector when determined relative to respective the keys; and a second plurality of optical fibers connecting the second row of optical fiber channels of the equipment-side connector to the row of optical fiber channels of the second trunk-side connector such that a left-to-right order of each of the second plurality of optical fibers is the same in both of the equipment-side connector and the first trunk-side connector when determined relative to respective the keys. The communication link also includes a first trunk cable and a second trunk cable, where each of the first trunk cable and the second trunk cable includes: a first trunk-cable connector including a key and a row of optical fiber channels positioned relative to the first trunk-cable connector key; a second trunk-cable connector including a key and a row of optical fiber channels positioned relative to the second trunk-cable connector key; and a third plurality of optical fibers connecting the row of optical fiber channels of the first trunk-cable connector to the row of optical fiber channels of the second trunk-cable connector such that a left-to-right order of each of the third plurality of optical fibers is the same in both of the first trunk-cable connector and the second trunk-cable connector when determined relative to respective the keys. The first trunk-side connector of the first breakout harness is connected to the second trunk-side connector of the second breakout harness at least partially via the first trunk cable, and the second trunk-side connector of the first breakout harness is connected to the first trunk-side connector of the second breakout harness at least partially via the second trunk-cable. 
     In another embodiment, the present invention is a communication link for use in a fiber optic communication network. The communication link includes a first breakout harness and a second breakout harness, each of the first breakout harness and the second breakout harness including an equipment-side connector, a first trunk-side connector, and a second trunk-side connector, the equipment-side connector having a first row of optical fiber channels and a second row of optical fiber channels, the first row of optical fiber channels being connected to the first trunk-side connector via a first plurality of optical fibers such that a left-to-right order of the first plurality of optical fibers in the first row of optical fiber channels relative to a key positioned on the equipment-side connector is the same as a left-to-right order of the first plurality of optical fibers in the first trunk-side connector relative to a key positioned on the first trunk-side connector, and the second row of optical fiber channels being connected to the second trunk-side connector via a second plurality of optical fibers such that a left-to-right order of the second plurality of optical fibers in the second row of optical fiber channels relative to the key positioned on the equipment-side connector is the same as a left-to-right order of the second plurality of optical fibers in the second trunk-side connector relative to a key positioned on the second trunk-side connector. The communication link also includes a first trunk cable and a second trunk cable, each of the first trunk cable and the second trunk cable including a first trunk-cable connector and a second trunk-cable connector, the first trunk-cable connector being connected to the second trunk-cable connector via a third plurality of optical fibers such that a left-to-right order of the third plurality of optical fibers in the first trunk-cable connector relative to a key positioned on the first trunk-cable connector is the same as a left-to-right order of the third plurality of optical fibers in the second trunk-cable connector relative to a key positioned on the second trunk-cable connector, the first trunk cable connecting the first trunk-side connector of the first breakout harness to the second trunk-side connector of the second breakout harness, and the second trunk cable connecting the second trunk-side connector of the first breakout harness to the first trunk-side connector of the second breakout harness. 
     In a variation of the above-described embodiments, the communication links described therein can be employed in a fiber optic telecommunication system for connecting together multiple pieces of telecommunication equipment such as, for example, patch panels and/or transceivers, while maintaining appropriate polarity. 
     These and other features, aspects, and advantages of the present invention will become better understood with reference to the following drawings, description, and any claims that may follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a front view of a 24-fiber transceiver receptacle. 
         FIG. 2  illustrates an interconnection system according to an embodiment of the present invention. 
         FIG. 3A  illustrates a harness used in the interconnection system of  FIG. 2 . 
         FIG. 3B  illustrates a front view of a 24-fiber connector used on one end of the harness of  FIG. 3A . 
         FIG. 3C  illustrates a front view of a 12-fiber connector used on another end of the harness of  FIG. 3A . 
         FIG. 4  illustrates the fiber routing scheme for the harness of  FIG. 3A . 
         FIG. 5  illustrates the lane routing from the first transceiver to the second transceiver shown in the system of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The system and methods according to embodiments of the present invention may be used to connect 24-fiber transceivers such as 100GBASE-SR10 transceivers. A general view of the transmit (Tx) and receiver (Rx) lanes of a 100GBASE-SR10 transceiver is shown in  FIG. 1 . In particular, the transceiver  100  includes a total of 24 fiber lanes aligned in two rows of 12 lanes. Reference to the top and/or bottom rows are expressed with respect to the key  105  positioned at the top of the connector. The top row  110  includes  12  lanes of which only the center  10  are used to receive optical signals. The bottom row  115  also includes  12  lanes and likewise uses only the center  10  lanes to transmit optical signals. Note that while the outside lanes are labeled as Rx 0 , Rx 11 , Tx 0 , and Tx 11 , these markings are merely for demarcation purposes and are provided to illustrate/denote the physical positioning of the channels. 
     Pursuant to IEEE 802.3 clause 86.6, the text of which is incorporated herein by reference in its entirety, there are no lane assignments for 100GBASE-SR10 transceivers, and instead, the transceiver hardware is expected to be able to map the appropriate electrical lanes to the appropriate optical lanes. 
       FIG. 2  illustrates an interconnection system  200  for connecting two transceivers  100 . For each transceiver  100 , the interconnection system  200  includes a breakout harness  205 . As shown in more detail in  FIG. 3A , the breakout harness  205  includes a 24-fiber connector  300  (e.g., MPO or MPO-style connector) on one end and two 12-fiber connectors  305  (e.g., MPO or MPO-style connectors) on the other end. The 24-fiber connector  300  is designed to mate with the 24-fiber transceiver  100 , and thus includes two rows of 12 fibers, as shown in  FIG. 3B . The top 12 fibers are routed to the first 12-fiber connector  305   Rx  and the bottom 12 fibers are routed to the second 12-fiber connector  305   Tx . The two 12-fiber connectors  305  are designed to mate with backbone/trunk cables, such as, for example, 12-fiber ribbon trunk cables. As shown in  FIG. 3C , both 12-fiber connectors have all 12 fibers positioned in a single row. Such configurations are commonly used with 12-fiber MPO or MPO-style connectors. 
     The fibers routed between connector  300  and connectors  305  may be ribbonized or they may be kept as lose fibers. Furthermore, the fibers are routed such that the fibers occupying positions 1-12 in connector  300  are routed to positions 1-12 in connector  305   Rx , respectively, and fibers occupying positions 13-24 in connector  300  are routed to positions 1-12 in connector  305   Tx , respectively. Note that the position of a fiber within a connector is expressed with reference to the connector key being positioned on the top and the numbering going from left to right starting at the top-most row. This routing scheme is detailed in Table 1 shown in  FIG. 4 . 
     Referring back to  FIG. 2 , the interconnection system  200  further includes two trunk cables/links  210  which link the trunk ends of the breakout harnesses  205 . Each trunk cable  210  includes a 12-fiber MPO or MPO-style array connector  215  at each end thereof and acts as a 1-1 cable (may also be known as a Type-A: 1-1 connector cable in the relevant art). Accordingly, optical fibers in positions 1-12 at one end of the cable are routed to positions 1-12, respectively, at the other end of the cable. Note, that while only one cable is illustrated between each pair of connectors  305 , this is merely exemplary, and other configurations which include more than one cable are within the scope of the present invention. To enable the trunk cable connectors  215  and the trunk end harness connectors  305  to mate appropriately, adapters  220  are used. The adapters  220  are key-up to key-down adapters which allow any of the mated connector pairs to align respective fiber positions (i.e., fiber positions 1-12 in a connector  305  respectively line up with fiber positions 1-12 in a mated connector  215 ). 
     To permit appropriate Tx-to-Rx routing between transceivers, connector  305   Rx  of the first breakout harness  205   1  is connected via the trunk cable  210   1  with the connector  305   Tx  of the second breakout harness  205   2 , and connector  305   Rx  of the second breakout harness  205   2  is connected via the trunk cable  210   2  with the connector  305   Tx  of the first breakout harness  205   1 . Furthermore, in order to maintain appropriate connector key orientation, each of the trunk cables  210  must include 1 (or an odd number of) twist(s)  225 . 
     The resulting transceiver-to-transceiver lane transition of the system  200  is shown in Table 2 of  FIG. 5 . As can be seen in Table 2, each Tx lane of transceiver  1  is paired up with an Rx lane of transceiver  2 . Likewise, each Tx lane of transceiver  2  is paired up with an Rx lane of transceiver  1 . 
     The system of the above-described embodiment and a method corresponding to the implementation of the system may be beneficial for a number of reasons. For example, the system  200  permits the use of a key-up to key-down connection scheme between the harnesses  205  and the trunk cables/links  210 . This scheme may improve signal transmission quality as it may allow the use of angled ferrules for connectors  305  and  215 . Furthermore, the system  200  permits the use of the same harness  205  for both ends of the interconnection link. This may help reduce errors during interconnection implementation where an installer may not be aware of the type of a harness installed on one end of the link. 
     While this invention has been described in terms of several embodiments, these embodiments are non-limiting (regardless of whether they have been labeled as exemplary or not), and there are alterations, permutations, and equivalents, which fall within the scope of this invention. Additionally, the described embodiments should not be interpreted as mutually exclusive, and should instead be understood as potentially combinable if such combinations are permissive. Moreover, any methods described or claimed, or that may be claimed should not be limited to any specific sequence of steps, and instead should be understood to encompass any sequence if such a sequence is allowable. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that claims that may follow be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.