Upgrading Path to High Speed Fiber Optic Networks

Transcription

1 SYSTIMAX Solutions Upgrading Path to High Speed Fiber Optic Networks White Paper April,

2 Contents Connectivity Method A 4 Upgrading Method A to Parallel Optics 4 Connectivity Method B 5 Upgrading Method B to Parallel Optics 6 Connectivity Method C 7 Upgrading Method C to Parallel Optics 7 Conclusion 8 2

3 The tremendous growth of information technology and bandwidth hungry applications, combined with continued increases in network traffic have driven the need for higher speed networks. Carriers, Internet Service Providers, Campus & Corporate backbones, and Data Centers are feeling the bottleneck effect of lack of bandwidth. This situation prompted the IEEE to form a High Speed Study Group (HSSG), whose sole responsibility is to form a new standard for 40 and 100 Gbps high speed Ethernet. As the standard starts to take shape, certain objectives are already established. The 40 Gbps segment of the standard will support distances of at least 100 meters on OM3 multimode fiber, at least 10 meters over copper, at least 1 meter over backplane copper, and at least 10 km on singlemode fiber. On the 100 Gbps side, the standard will support distances of at least 40 km on singlemode fiber, at least 100 meters on OM3 multimode fiber, and at least 10 meters over copper. The standard is expected to be ratified by When network architects design a new project, whether it is a data center, backbone infrastructure, or a campus layout, they need to take under consideration the possible migration to higher speed networks. Currently LC connectors are the most commonly used optical connector type within the transceivers (Switches, Routers, Transport Devices, etc.). However when the 40 and 100 Gbps protocols are implemented, the equipment manufacturers will most likely start using array type connectors (MPO) and a parallel optics architecture. The array connectors, which generally use 12 fibers in a single connector ferrule, will allow aggregation of 10 Gbps signals to compile the 40 and 100 Gbps speeds. Figure 1 illustrates the fiber strand lane arrangement within the 40 Gbps MPO connector, where fibers 1 through 4 are identified as Tx (transmit) 1 through 4, fibers 5 through 8 are unused, and fibers 9 through 12 are identified as Rx (receive) 4 through 1. The signal lane arrangement for 100 Gbps has not yet been defined, but most likely will use one MPO connector for transmit and one for receive. With array connectors, polarity management (ie, transmit-to-receive and receive-to-transmit signal paths) is key to ensure the correct connectivity between two transceivers. The ANSI/ TIA/568-C.0 and C.3 standards provide three polarization methods (method A, B, and C) for cabling terminated with MPO connectors. Methods A and B include two options: one utilizing LC connections in the transceivers, and the other utilizing parallel optics with MPO connections in the transceivers for implementing 40 and 100 Gbps high speed networks. In order to upgrade using method C for parallel applications, the trunk cable must be replaced or concatenated with a second Type-C trunk, due to the fact that it uses an unconventional wiring configuration (see figure 7). This paper discusses the pros and cons of these connectivity types. Fiber # Signal 1 Tx1 10g 2 Tx2 10g 3 Tx3 10g 4 Tx4 10g 5 unused 6 unused 7 unused 8 unused 9 Rx4 10g 10 Rx3 10g 11 Rx2 10g 12 Rx1 10g Figure 1 40 Gbps Signal Lanes 3

4 Connectivity Method A Using this type of connectivity, a Type-A array trunk cable connects to an MPO module on each side of the link. This trunk cable, which is terminated on one end with the MPO connector in a key-up orientation and on the other end with the MPO connector in a keydown orientation, is connected between two identical MPO modules. The polarity management routing of signals from transmitters to receivers is not handled in the trunk, or in the MPO modules. Instead, two types of patch cords must be used in order to correct the polarity, and ensure that the transmit signal on one side of the link is routed to the receiver on the other. In figure 2 the patch cords on the left are standard duplex A-to-B LC type, whereas the patch cords on the right a non typical duplex A-to-A LC type must be employed in order to ensure the correct the polarity. Note: The trunk cable is illustrated with a twist in order to show the keys on both sides Figure 2 Connectivity Method A for two-fiber applications Upgrading Method A to Parallel Optics In order to convert this infrastructure to parallel optics for 40 and 100 Gbps operation, the MPO modules and LC patch cords are removed, and must be replaced with MPO adapter panels containing opposed-key type adapters, and MPO patch cords. There is no need to replace the main trunk cable. To route transmitted signals to receivers, two types of MPO patch cords are used Type-A on the left, and Type-B on the right (figure 3). These differ by the orientation of the MPO plugs on either end. Using two patch cord types creates additional design & logistics work and confusion during the ordering, delivery, maintenance, and installation processes. Figure 3 Connectivity Method A Parallel Optics 4

5 Connectivity Method B Using this type of connectivity, a Type B array trunk cable connects to an MPO module on each side of the link. This array cable is terminated with MPO connectors in key-up orientation on both ends. The two identical MPO modules are positioned in their panels in opposite orientations - one with the LC adapters key-up and the other with the LC adapters key-down (as indicated in figures 4 & 5). The labels on these modules indicate port numbers for both orientations (1-12 for Alpha on one side of the panel, and 1-12 for BETA on the other side). The combination of the Type-B trunk cable, and the reverse orientation of the MPO modules, ensures the correct polarity of the transmit/receive signals. Therefore standard A-to-B type duplex patch cords are used on both sides to connect to the transceivers. Note: The trunk cable is illustrated with a twist because the right module is rotated to place LC keys down Figure 4 Connectivity Method B for two-fiber applications ALPHA ALPHA BETA BETA Figure 5 Same Modules Reversed Orientation 5

6 Upgrading Method B to Parallel Optics In order to convert this infrastructure to parallel optics, the MPO modules and LC patch cords are removed, and replaced by MPO adapter panels containing aligned-key type adapters, and MPO patch cords. There is no need to replace the main trunk cable. The combination of Type-B trunk key-up to key-up cable, and aligned-key MPO adapters ensures the correct polarity of the transmit/receive signals, independent of the number of cables and cords employed in the channel. In this connectivity method, only one type of MPO patch cord is used (Type-B) on both sides (figure 6). Figure 6 Connectivity Method B Parallel Optics Connectivity Method C Using this type of connectivity, a Type-C array trunk cable is connected between the two MPO modules. The Type C array trunk cable has a unique configuration where each of the 6 fiber pairs is reversed (figure 7) in order to route the transmitted signals to receivers, pair by pair. Figure 7 6

7 The pair-reversed trunk cable, which is terminated on one end with the MPO connector in a key-up orientation and on the other end with the MPO connector in a key-down orientation, connects to two identical MPO modules. Patch cords at both ends are the standard duplex A-to-B LC type (figure 8). Note: The trunk cable is illustrated with a twist in order to show the keys on both sides the right module is rotated to place LC keys Figure 8 Connectivity Method C for two-fiber applications Upgrading Method C to Parallel Optics There are two ways to upgrade this connectivity to parallel optics, both are complex. One way is to remove the trunk cable, and replace it with a standard Type-B trunk cable. The MPO modules and LC Duplex patch cords also need to be removed and replaced with Type-B array patch cords and aligned-key MPO adapters. This means that the complete infrastructure must be removed and replaced with connectivity method B as indicated in figure 6. The other way involves adding another Type-C trunk to reverse the pairs back to normal. Each added Type-C trunk either inserts or removes the pair reversal. Odd numbers insert a reversal, while even numbers of trunks remove the reversal. Since this method is rather complex, and adds a sizeable insertion loss with each trunk, the standards committee elected not to address it. Therefore a parallel application for Method C is not included in the TIA standard. Conclusion Of the three methods described above, both Methods A and C are complex, and are difficult (and costly, in both time and money) to upgrade to high speed networks. Method A requires the use of two types of patch cords to ensure transmit/receive connectivity, as well as two types of MPO cords when upgraded to parallel optics. Method C utilizes a special trunk cable, which must be replaced or used with a patch cord containing Type-C trunk pair reversals when migrating to parallel optics. Even numbers of such pair reversals are required for proper connectivity, making this method similar to Method A with respect to imposing extra complexity in day-to-day circuit administration. Visit our Web site or contact your local CommScope representative for more information CommScope, Inc. All rights reserved. All trademarks identified by or are registered trademarks or trademarks, respectively, of CommScope, Inc. This document is for planning purposes only and is not intended to modify or supplement any specifications or warranties relating to CommScope products or services. 08/11 Since, connectivity Method B utilizes the MPO module s orientation during installation, and keyup to key-up termination and adapter keying, it extends to array connectivity the signal routing principals long established for duplex fiber systems in structured cabling standards. Method B requires no special patch cords or trunk cables, provides correct polarity independent of the number of concatenated segments, and provides the easiest path to parallel optics. CommScope InstaPATCH Plus system uses Method B for array connectivity, which guarantees the correct transmit/receive polarity, as well as paves the right migration path to high speed networks. Some manufacturers offer additional designs for array cabling systems that are proprietary (patented), and therefore haven t gone through public review. Unlike standards-adopted methods, proprietary methods are generally only available from a single manufacturer.