Using Laser-Optimized Multimode Fiber for 1 and 10 Gigabit Campus Backbone Applications

Transcription

1 Using Laser-Optimized Multimode Fiber for 1 and 10 Gigabit Campus Backbone Applications David Kozischek, Market Manager Enterprise Networks, Corning Optical Communications Systems engineers at Corning are routinely asked these two questions: 1. How do I determine the type of fiber needed for my campus backbone? 2. How do I determine the number of fibers needed for my campus backbone? Both of these questions require analysis to help the network designer make the best decision. This paper provides design guidance by putting analysis behind the decision-making process, including: 1. Fiber types used in the campus backbone 2. Designing the cabling infrastructure 3. Determining the fiber type and fiber mix for 1 and 10 Gigabit Ethernet (GbE) 4. Determining the total fiber counts 5. Final fiber count and fiber mix 6. Single-mode fiber vs. high-performance multimode fiber 7. Rules of thumb This paper uses a network model to evaluate different installation scenarios based on 1 and 10 GbE as the local area network (LAN) protocol and analyzes the benefits of using laser-optimized 50 µm multimode fiber in these networks. 1. Fiber Types Used in the Campus Backbone Before Gigabit Ethernet (GbE), fiber type was an easy decision in campus design. Standard 62.5/125 µm multimode fiber (OM1) was used for any application up to 2000 m and network speeds up to OC-12 (622 Mbps) and single-mode fiber was used for anything else. Gigabit (Gb) and changed these rules. Laser-optimized 50 µm multimode fiber (OM3, OM4) was introduced with increased bandwidth performance for, and the fiber performance was included in the ANSI/TIA-568 Standard. A summary of the fiber types and their optical performance is shown in Table 1. Litcode-##-EN LAN-1592-EN Page 1

2 Type Description OFL EMB Multimode Single-mode OM1 OM2 OM3 OM4 Standard 62.5/125 μm Standard 50/125 μm Laser- Optimized 50/125 μm Laser- Optimized 50/125 μm MHz km at 850 nm MHz km at 300 nm MHz km at 850 nm db/km at 850 nm db/km at 1300 nm Attenuation 850 nm 850 nm OS2 Standard SM N/A N/A N/A Table 1: Corning LANscape Solutions Cabled Fiber Types Different fiber parameters are shown in Table 1. Overfilled launch bandwidth (OFL BW) is used for light-emitting diode (LED) electronics operating over multimode fiber. The effective modal bandwidth (EMB) simulates operation on multimode fiber based on the use of Gb or vertical-cavity surface-emitting lasers (VCSELs) at 850 nm. 2. Designing the Cabling Infrastructure Before attempting to determine the fiber types, determine the cabling topology for the campus. To do this we will create a campus backbone model. The backbone model assumes each building contains multiple floors with a minimum of one telecommunications room (TR) per floor. All distances are in meters and include the length from the building entrance to the main communications room. All network analysis is based on a GbE building-to-building fiber backbone with provisions for. The design of the cabling topology can be separated into three smaller steps to help the network designer make the best choice. These steps include: A. Consult the TIA-568 Standard. B. Determine the location of the main cross-connect (MC), intermediate cross-connects (IC), and horizontal cross-connects (HC). C. Determine the fiber distances. Let s look at each of these steps. LAN-1592-EN Page 2

3 A. Consult the TIA-568 Standard The standard gives design rules for cabling the campus backbone. They include: The backbone cabling shall use hierarchical star topology. There shall be no more than two levels of cross-connects. Connections between any two HCs shall pass through three or fewer cross-connects. Maintain length requirements between the MC, IC, HC and in accordance with ANSI/ TIA-568-C, where cable lengths are dependent upon the application and upon the chosen media type. B. Determine the location of the MC, ICs, and HCs Before determining the location of the MC, ICs, and HCs, define the function of these cross-connects. The MC is a cross-connection for first-level backbone cables, entrance cables, and equipment cables. The IC is a cross-connection between first and second-level backbone cabling. The HC is a cross-connect of horizontal cabling and other cabling, such as backbone or equipment cabling. In the campus model, assume each TR will act as the HC and connects to the building IC. Next, the ICs connect back to the MC in a physical star topology. The key decision is how to determine the location of the MC. The location of the MC can be dictated by where most of the servers, switches, and routers are housed. If a certain building is already chosen based on these criteria, then all length calculations would be from that point. If any of the buildings can act as the MC, determine which building is centrally located in order to minimize cable lengths. Selecting the Administration (Admin) Financial building as the MC and the other buildings as ICs yields a practical solution, since it is centrally located on the campus. The cable route and distance is shown in Figure 1. Campus Network Model Physical Cable Topology IC Admin m Admin 1 IC 190 m 190 m Admin 2 IC Cable Admin Financial MC Handhole Conduit 230 m Admin 4 IC Figure 1 LAN-1592-EN Page 3

4 C. Determine the fiber lengths Though the cable is deployed as a physical star, other logical topologies can be considered, such as a ring and mesh network. To get a better understanding of the fiber distances, it is a good idea to construct a matrix that defines the fiber distance between any two buildings in the backbone. Remember that the Admin Financial building is the MC for our campus, so all network connections flow through the MC. Table 2 illustrates this concept for our campus model. Length Calculator in meters To From Admin Fin Admin 1 Admin 2 Legal Observ Admin Fin Admin Admin Admin Admin Table 2: Fiber Matrix 3. Choosing the Fiber Type and Fiber Mix for 1 and 10 Gigabit Ethernet Based on the cable routes chosen for our campus model, the next step is to determine the fiber types. Since we are concentrating on the campus backbone (building-to-building links) and Gb and technologies, we need to look at length restrictions based on fiber type. This comparison is shown in Table 3. This type of analysis should also be used for the building backbone. Type Multimode nm OM1 Standard na OM2 Standard na OM3 Laser- Optimized na OM4 Single-mode Laser- Optimized nm OS2 Standard SM 5000 N/A Table 3: Corning LANscape Solutions Cabled Fiber Types LAN-1592-EN Page 4

5 The GbE distances shown in Table 3 are a function of the fiber core type and the associated effective modal bandwidth (EMB). Though OM1 µm fiber has a larger installed base, is it worth switching over to 50 µm (OM3 only)? Also, what should the fiber mix of multimode to single-mode be? To answer these questions, we will apply a logical networking scenario to the physical topology. In the campus model, a redundant point-to-point logical star topology is implemented. This architecture uses redundant electronics in all buildings to reduce single points of failure. In this example the campus backbone is sized for with provisions for a network. The first step in implementing this architecture is to determine the fiber counts for the GbE backbone. The assumptions in Table 4 are used to determine the fiber count per link. Since the logical topology is a point-to-point, the distances shaded in Table 2 are used. In the analysis that follows, we are going to look at migrating the backbone from one to four Gigabits using standards-based (IEEE 802.3ad) Ethernet trunking. The campus will also utilize two switches per building. We will not consider trunking at this time. To analyze this network, look at how many fibers and what type of fibers (multimode and single-mode) are lit in migrating the network to the logical topology shown in Figure 4. Look at multiple building-to-building (MC to IC) links, and calculate the number of fibers utilized. Table 4 illustrates that 16 fibers are needed for each building-to-building link for the 4 GbE backbone: Two links per building x two fibers per GbE link x four GbE trunk per link = 16 fibers. This also shows that to implement a redundant star topology, four fibers are needed for each building-to-building link for migration. Data Ethernet GbE Backbone Fiber Count Calculator Point to Point Number of Distribution Switches per IC 2 Number of Core Switches per MC 2 Ethernet Trunking (maximum Gb/s) 4 Minimum Ethernet Fiber Count from IC to MC 16 Minimum Ethernet Fiber Count from IC to MC 4 Table 4: GbE and Fiber Counts 4. Choosing the Total Fiber Counts The next step is to determine the number of multimode and single-mode fibers that are needed to implement this redundant star topology. This is accomplished by referring back to Table 2 for the building-to-building link lengths and comparing the fiber type to the length restrictions for 1 GbE and in Table 3. LAN-1592-EN Page 5

6 Analysis is then conducted, trying to size the backbone to maximize the use of 850 nm VCSELs for serial GbE and. Even though multimode fiber can operate at the 1300 nm window for GbE and, it is more cost-effective to operate at 850 nm over multimode due to the lower cost of the transceivers. The last step is to determine the final fiber counts for each cable. Table 4 gave us the minimum fiber counts to migrate the backbone trunk from 1-4 GbE with migration to, but what about other applications that might run across the network? Applications such as security video, card readers, video conferencing, and control systems are applications that require additional fibers. Unless all applications are going to operate over an IP network, you will also need to add spare fibers in the cables. Spare fiber can run anywhere from 25 percent up to 100 percent in a campus design. In this campus model a 50 percent spare rule is used. With this information the fiber matrix illustrated in Table 5 was generated. Campus Backbone Spare % Total Fiber Counts 50% 50% IC MC GbE Fiber Count From To OM1 OS2 Admin 1 Admin Fin 16 0 Admin 2 Admin Fin 16 0 Admin 3 Admin Fin 16 0 Admin 4 Admin Fin 16 0 From To OM2 OS2 Admin 1 Admin Fin 16 0 Admin 2 Admin Fin 16 0 Admin 3 Admin Fin 16 0 Admin 4 Admin Fin 16 0 From To OM3 OS2 Admin 1 Admin Fin 16 0 Admin 2 Admin Fin 16 0 Admin 3 Admin Fin 16 0 Admin 4 Admin Fin 16 0 From To OM4 OS2 Admin 1 Admin Fin 16 0 Admin 2 Admin Fin 16 0 Admin 3 Admin Fin 16 0 Admin 4 Admin Fin 16 0 From To MM OS2 Admin 1 Admin Fin 0 16 Admin 2 Admin Fin 0 16 Admin 3 Admin Fin 0 16 Admin 4 Admin Fin 0 16 Fibers Table 5: Fiber Count and Fiber Mix Breakdown Spare Fibers OM1 OS2 OM1 OS2 OM2 OS2 OM2 OS2 OM3 OS2 OM3 OS2 OM4 OS2 OM4 OS MM OS2 MM OS Total Fibers Recommended Count OM1 OS2 OM1 OS2 OM2 OS2 OM2 OS2 OM3 OS2 OM3 OS2 OM4 OS2 OM4 OS MM OS2 MM OS LAN-1592-EN Page 6

7 Table 5 shows the fiber count and fiber mix breakdown based on the different fiber types. As shown, the fiber mix can change based on the type of multimode fiber and the length restrictions for 1 and. To determine which fiber mix is the most effective price, analyze the price of the GbE transceivers, transceivers, and the fiber types for this campus backbone. Prices are as follows: Cables that contain OM1 or OM2 are assumed equal in price. OM3 and OM4 have an associated premium. This price is based on list pricing. LX cards for GbE over single-mode fiber typically cost two times more than the GbE SX cards for multimode fiber. This is based on list price. LR cards for over single-mode fiber typically cost two times more than the SR cards for multimode fiber. This cost is based on list price. The results are shown in Figure 2. For this network topology, using a hybrid cable containing laser-optimized OM4 multimode fiber is the lowest cost solution vs. other cable mixes. The reason that the laser-optimized fiber is the most advantageous is that more links are using 850 nm for GbE and migrate Ethernet trunks from 1 to 4 Gb/s and then install a network. The other item to note on the graph is that the laser-optimized OM4 multimode fiber solution is 30 percent cheaper than operating this network over only single-mode fiber, even though the cable cost is higher than the other solutions. Even though the single-mode fiber can support up to 5 km, and up to 10 km at 1310 nm, the higher premium paid for the solution is a direct result of the much higher price of the and cards that operate over the single-mode fiber. GbE Trunk and Price Analysis-Cable and Electronics High Cost Elec Cable Low Cost OM1/SM OM2/SM OM3/SM OM4 SM Fiber Mix Figure 2: Price Analysis Based on Fiber Mix 5. Final Fiber Count and Fiber Mix After adding the spares, the cable counts were sized at 36 OM4 multimode fibers. Distributors typically stock cables that are multiples of six or 12 fibers. LAN-1592-EN Page 7

8 6. Rules of Thumb Though there are many different types of fiber, some simple rules can be applied to help network engineers design local area networks (LAN). Table 6 illustrates some basic rules that can help determine when to use a certain fiber in a LAN. IF Link is Then for 1 GigE Use Then for 10 GigE Use Where < 150 m OM4 OM4 Data Center 150 m-300 m OM4 OM4 Data Center and Building Backbone 300 m-550 m OM4 OM4 Building Backbone and Small Campus Backbone 550 m-1000 m SM SM Campus Backbone > 1000m SM SM Campus Backbone Table 6: Fiber Mix Rules of Thumb Table 6 shows that for links less than or equal to 550 m, a laser-optimized 50 µm multimode fiber should be considered for 1 and applications. This table is based on being able to migrate the network from 1 to and maintaining consistency in the fiber mix. Special considerations are required for 40/100G migration. Consult ES for guidance. Conclusion In summary, a couple key points can be drawn from this analysis to help make the best decision when determining fiber types and fiber counts for a campus network. 1. Use the standards. They were created to protect the end user. 2. Do some analysis. Understand the network applications and possible traffic growth. 3. Understand the physical topology and the logical topology. 4. Examine where you can save money MC selection, electronics choice and cable routing. 5. For distances less than 550 m, a laser-optimized multimode fiber may yield a price savings compared to a SM solution. Corning Optical Communications LLC PO Box 489 Hickory, NC USA FAX: International: Corning Optical Communications reserves the right to improve, enhance, and modify the features and specifications of Corning Optical Communications products without prior notification. A complete listing of the trademarks of Corning Optical Communications is available at All other trademarks are the properties of their respective owners. Corning Optical Communications is ISO 9001 certified. 2013, 2015 Corning Optical Communications. All rights reserved. Published in the USA. LAN-1592-AEN / January 2015 LAN-1592-EN Litcode-EN Page 82