Kurt Templeman, Director of Applications Engineering, Sumitomo Electric
Introduction
Passive Optical Networks (PONs) have been used in the deployment for FTTH and service provider networks for many years. Until recently, PONs have not been widely used in enterprise networks. For many customers in a wide range of vertical markets, the time has come to evaluate PON/POL (passive optical LAN) and Air-Blown Fiber®* (ABF) networks in their enterprise applications.
The PON has become recognized for providing significant cost savings, reliability, and ease of physical redundancy. Coupled with the speed, real-time scalability, future proofing, and further cost savings of AirBlown Fiber, the marriage of PON and ABF deliver the optimal performance and cost efficiencies required by today’s continually changing, high gigabit speed, and bandwidth hungry networks.
Network Design – Traditional Enterprise Network vs PON
Traditional LANs for the enterprise space are a hierarchy of electronics that provide the switching functions with typically multiple cable infrastructures, and multiple network topologies supporting voice, data, video, and other applications. These traditional infrastructures may utilize Cat X, twisted pair, coax or even fiber, which in most cases has been multimode fiber. The use of single-mode fiber has been mostly in the backbone when it has been deployed. Refer to Figure 1 below.
The PON is a network that uses point-to-multipoint fiber topology in which unpowered optical splitters are used to enable a single optical fiber to serve multiple devices. PONs may reduce the number and or size of the telecommunication room (TR) that supports your current enterprise topology. The reduction in the number of TRs, the space saved, and the elimination of the remote electronics will greatly reduce the power required in the telecommunication rooms. The subsequent reduction in heat generated within the TR can be of enormous benefit to the facility, as well. The PON can also change the dynamic allocation of human resources, which have been used in the past, to constantly address moves, adds and changes (MACs) in the network and trouble shooting. The dynamic allocation of bandwidth can quickly meet the every changing demands of the enterprise with all of its bring-your-own-devices (BYOD) demands for greater bandwidth and connectivity.
The PON/POL designed for the enterprise market consists of the optical line terminal (OLT) at the core/main data center, passive optical splitters at an aggregation point (Figure 2 shows a typical splitter module), and optical network terminal (ONT) or optical network units (ONUs) at the access points.
The passive optical network uses single-mode fiber (SMF) for the transport media and converges all the building or campus ICT services into a single network. PON technology uses SMF, which is necessary to enable wave division multiplexing (WDM) of the upstream and downstream signals. The passive optical splitters utilized in the PON divide the signal from a single port from the OLT into typically 32 ONTs, which are typically collocated near the work group areas. The fiber connectors used in the deployment of the PON are primarily SC/APC and are a recognized and widely implemented connector type. Refer to Figure 3 below.
Benefits of an Implemented POL/PON:
Reliability—PON equipment is typically 5-9s (99.999%) available
Ease of Administration and Maintenance —since there is less active equipment to inspect, administer, and maintain, the PON typically generates significantly reduced annual maintenance costs. With an all fiber network, maintenance issues are much less than with copper cabling that has a 7 to 10 year life span vs 25+ years associated with the fiber network.
Energy savings —reduction in the number of rack mount switches and other active devices in remote locations will eliminate a number of heat generating devices that must be cooled and powered, thereby generating sizable energy savings. Also, there are reduced HVAC requirements, since there is no radiant heat with fiber cabling.
Minimize resources for support —central management of the network minimizes the support requirements and facilitates easier network moves, adds & changes.
Optimized bandwidth utilization—with dynamic allocation of bandwidth, the system can provide optimized network connectivity to those application and users requiring the greatest bandwidth, while facilitating future proofing.
Eliminates the need for multiple platforms—the PON was designed to provide 1 network for all services including VoIP, video, and data. For example, PON enables analog voice to be converted into VoIP directly within the ONT, allowing both analog POTS and VoIP to be carried through the PON network identically. Moreover, the carrying of CATV signals is transparent in the passive optical network.
Lower cost of total ownership—the total cost of ownership (TCO) is not only the matter of the cost of the electronics, blades, network interconnect cards, cable plant, and the installation of all, but is also in reality the cost of all the capital expense (CapEx) items. Due to lower power consumption, reduction in floor space, and yearly reduced maintenance costs, the enterprise will realize significant operational expense (OpEx) savings over the life of the system of 45-70% over that of a traditional copper based system, as well. The differences between a traditional network and a PON system are further explained in the illustration below in Figure 4.
The remote electronics being eliminated through the use of PON vs traditional systems are the remote edge switches and other equipment being used to implement and control the optical fiber to copper conversion. In addition, the distance capabilities of a PON system eliminate the restrictions inherent in copper or even in MMF networks. The human resources can then be redeployed to perform network performance improvements, application software refinements, and other tasks for which they are uniquely qualified to perform.
The Addition of Air-Blown Fiber
The addition of air-blown fiber into the traditional network provides those networks with the ability to quickly, easily and economically provide fiber on demand and to meet the ever changing topologies and network requirements by blowing fiber bundles into previously installed tubes. Fiber bundles with 2, 4, 6, 12, 18 or 24 fibers can be installed in minutes instead of days weeks or months as with conventional fiber cable.
The traditional LAN also had the requirement for any number of different types of fibers with the network to support different system requirements. In addition to single-mode fiber (SMF) OM1, OM2, OM3 & OM4 have been required to support various systems. Although a PON will only require SMF, the potential for an existing network to install PON in a phased in approach is very real. The use of ABF allows the customer to maintain their current system while simultaneously deploying the new fiber for the PON application. ABF greatly aids in the ability to provide this fiber as needed and as systems are phased over to the PON.
One argument against the use of PON in the enterprise market has been the relatively long time to repair or replace any fiber cut. With ABF, this issue has been resolved because with Sumitomo’s FutureFLEX® Air-Blown Fiber® repairs can be made quickly to the tube cable and new fiber bundles can be installed at 100-150 feet per minute. Old fiber bundles can be removed or quickly blown out undamaged and reused in other deployments, thereby providing new fiber end to end in minutes. In addition, PON architectures can be provided that further address this issue by simple link or equipment duplication, thereby providing the fault tolerance required for some networks.
The benefits of an air-blown fiber system are:
· Provides flexibility by either eliminating the need for both conduit and innerduct, or the significant reduction of both in pathway Infrastructure design
· Supplies virtually unlimited pathway, fiber and bandwidth capacity, solving filled conduit and duct bank problems
· Provides Real-Time, On-Site network scalability for fiber installations and MACs anywhere and anytime in the network for an already future proofed network
· Eliminates physical disruption to the facility and re-entrance into ceilings, walls, and maintenance holes
· Offers a point-to-point (PTP) continuous splice-free optical fiber run, eliminating potential points of network failure
· Drives fast and easy optical fiber installations, upgrades, and MACs in secure, hazardous and hard-to- reach areas in MINUTES
· Delivers an environmentally friendly optical fiber installation system that is reusable, renewable, and sustainable with no end to the fiber or bandwidth life cycle
· Saves typically 70 to 90 percent of the time and cost associated with conventional cabling systems for optical fiber-related projects and generates continuous return on investment (ROI)
The ABF Tube Infrastructure
At the heart of the blown fiber system is an infrastructure of tube cable, available in a wide variety of ratings, including outdoor, outdoor/indoor, and indoor ratings. These tubes form the intra-building and inter-building topology, ultimately providing virtually unlimited optical fiber, bandwidth and pathway capacity.
The Installation of the tube cable is the only occurrence of physical disruption to the building, campus and/or its grounds. The tube cable contains smaller empty tubes and can be direct buried in the outside plant, reducing labor intensive work in maintenance holes for upfront infrastructure cost savings.
The tube cable is also flexible enough to be placed in an existing conduit pathway. To illustrate the extent of the capacity provided by the tube cable, consider that in a 4 inch conduit a total of only three 1.25 inch innerducts can be installed—through which conventional optical fiber cable is pulled—yielding only three pathways in the conduit. In that same conduit, two blown fiber 19-tube cables yield 38 optical fiber pathways. This ultimately resolves congested conduit and increases the likelihood of never having to install additional conduit. See image 1 below.
Some users will wish to deploy a phased in approach in that they will begin to make the transition from the traditional Ethernet switch network to a PON system either by floor or by building in the case of a campus. The ABF system makes this desire a valid and viable option. By installing tubes from the end of the first phase to the next phase, installers are able to blow in the requisite fiber from the farthest point all the way back to the OLT.
The use of ceiling mounted panels, which house the aggregate splitters or FDHs (fiber distribution hubs) and/or ONUs, can eliminate the need for building a TR and make that space available for other purposes. As the demand increases, additional fibers may be blown into the previously installed tubes to provide additional connectivity.
The design effort required to implement a PON system is quite simple. Since the core switch location is one of the first steps to consider, and that location is most typically where the current Ethernet switch is located, then the design of the remaining plant is less complex than with the traditional switched Ethernet network. You no longer must be concerned with all the supporting systems required for the traditional system, such as power, space & cooling. When again referring to Figure 4, the differences become quite apparent. Through the use of a zone approach, you can place the FDHs in housings in the ceiling or in wall or rack mounted housing that utilize less space and can easily be concealed.
Once the overall design of the termination locations is completed, then the designer will layout the Air-Blown Fiber tube cable infrastructure required to support the smaller fiber bundles needed to support the network. The design criteria used to implement a FutureFLEX Air-Blown Fiber system in support of a PON network is the same as used with a traditional network. The real difference in the design will be the significant reduction in the number of tubes/fiber pathway and optical fiber required to support the system day one. The FutureFLEX system will continue to allow the designer/installer or end user the ability to add FDHs, ONTs or ONUs easily, quickly, and economically as the network demands dictate with no physical disruption to the facility, its grounds, or its daily operations.
CONCLUSION
The use of PON and ABF together can provide a network that is more flexible, immediately scalable, most cost effective, and easier to manage than any other optical fiber cabling option. While the same advantages of an ABF system will be enjoyed in both a traditional network and a PON, the combination of the PON and ABF will provide the end user with a robust cable plant and transport system with the greatest flexibility to meet quickly and easily the ever changing demands of the enterprise network.
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