F-NET NETCONNECT XG FIBER SYSTEM

INTRODUCTION

If history is any indication, network applications will continue to demand higher data transfer rates. New applications such as high-resolution graphics and complex scientific modeling continue to pressure bandwidth requirements at the desktop and backbone. Increases in the number of high bandwidth applications, the number of users and the volume of network traffic dictate that old 10Mb/s Ethernet and 100 Mb/s Fast Ethernet LANs will be replaced with even higher speed LAN connections. Fibre Channel networks, too, are migrating to faster data rates, and LAN applications are evolving to cover the WAN and even access applications like fiber to the home. Conclusion: network managers have to look for even higher data rates in backbone connections.

Many network owners have turned to Gigabit Ethernet (1000 Mb/s) to maintain acceptable LAN performance levels. While the need for a gigabit “pipe” to the desktop may be overkill today, the rapidly decreasing price differentials between Fast Ethernet and Gigabit Ethernet make an effective argument for installing Gigabit Ethernet today as an inexpensive insurance policy against future re-cabling headaches. However, just as the growing number of Fast Ethernet connections created the need for Gigabit Ethernet connections in backbone applications, so too has Gigabit Ethernet created the need for Ten Gigabit Ethernet (10000 Mb/s).

Ten Gigabit Ethernet (10GBASE-X) provides the solution for high-speed backbone connections as a natural upgrade for extending the existing network investment to ten gigabit per second speeds at a reasonable cost without the need to re-educate support staff. The IEEE 802.3ae task group spent over two years developing the Ten Gigabit Ethernet Standard, which was published in 2002. The Standard provides the opportunity to significantly increase the system bandwidth while maintaining compatibility of the installed base of Ethernet.

The convenience of a one-fiber-fits-all solution is inestimable, and was developed along with the 10 GbE Standards. The F-NET NETCONNECT XG Fiber System provides a migration path from 10 Mb/s all the way to 10 Gb/s on the same fiber, using the lowest-cost wavelength (850nm) for the complete horizontal and riser network. The XG Fiber System offers the high bandwidth ‘850nm laser-optimized 50/125µm’ fiber cables and the connector components capable of running 10 Gigabit applications, such as Ethernet and Fibre Channel, for distances of 2 to 300 meters at a wavelength of 850nm. This same fiber supports legacy applications just as well or even better than the standard laser certified 50/125µm fibers. Install the XG fiber today, use it today, and use it for future equipment upgrades to 1 and 10 Gb/s.

HISTORY

Gigabit Ethernet and now 10 Gigabit Ethernet demand fast optical sources to support the rapid modulation rates necessary for intelligible bit streams, yet still need the low-cost advantages that propelled Ethernet to become the most popular LAN application. The traditional and inexpensive light-emitting diode (LED) can be utilized only for applications running up to 622 Mb/s -the output is unreadable at faster data rates. Single-mode lasers, capable of higher speeds, have been available for many years, but are much more expensive than the common LEDs. Fortunately, the industry developed and refined a cost-effective laser technology called the VCSEL (Vertical Cavity Surface Emitting Laser) for short wavelength (850nm), high-speed data applications.

Of course, a source is only as good as its coupled fiber. The standard 62.5/125�m and 50/125�m fibers were fine for use with LED sources with their overfilled launches. The newer laser certified multimode fibers are generally sufficient to support VCSELs used for Gigabit Ethernet and similar data rates for LAN networks. However, to take advantage of 10Gb/s VCSEL technology, a higher bandwidth fiber had to be developed to reach the same distances.

Physical limitations prevent a 62.5/125µm multimode fiber from providing bandwidth this high in the 850nm window, except in rare cases. A 50/125�m fiber typically offers higher bandwidth, but is designed with an index of refraction profile that provides optimum bandwidth near 980nm, providing good bandwidth at both the 850nm and at 1300nm wavelengths – the two operating wavelengths for premises optical networks (this explains why standard 50/125�m fiber offers equal bandwidth for both wavelengths, typically 500 MHz·km). However, the models show that 500 MHz·km is not sufficient for 300 meters of 10 Gb/s. In fact, neither is 1000 MHz·km, nor even 1500 MHz·km. To support 10 Gigabit Ethernet and 10 Gigabit Fibre Channel to the full 300 meters, 2000 MHz·km bandwidth is needed at 850 nm. Unfortunately, the normal production of 50/125�m fiber is unlikely to produce a fiber of this bandwidth, so a change was needed.

The result was the “850nm laser-optimized 50/125µm fiber” – fiber produced by making small changes in the index of refraction profile (the fiber core’s index of refraction vs. core position) of a 50/125µm fiber to provide the maximum bandwidth at 850nm, rather than 980nm. With this change, it became possible to produce fibers with the minimum bandwidth needed to support 10Gb/s applications to the full 300m distance of structured cabling building backbones. This fiber, specifically designed to work with the 850nm VCSELs was optimized for these sources – 850nm laser optimized.

Even that was not enough to ensure the necessary operation. The traditional overfilled launch (OFL) bandwidth measurement could not assure that a 2000MHz·km fiber would support a 10Gb/s application. Because VCSEL sources only partially fill the multimode fiber core with light, it is much more susceptible to perturbations in the optical fiber's index of refraction profile. These perturbations, a consequence of the manufacturing process, are most pronounced in the centerline of the fiber - at the point where the VCSEL launches. Instead of OFL, a measurement method was developed that approximates a laser launch and compensates for the light power distribution in the core. Now, it is easy to determine the ability of a fiber to support 10Gb/s data rates for the 300m distance.

This fiber, called 850nm Laser-Optimized 50/125�m Multimode Fiber, or OM-3 fiber, in the standards, is now available for the networks of today and tomorrow. At AMP NETCONNECT, this fiber is our standard XG Fiber.

WHY 850NM LASER-OPTIMIZED 50/125 µM MMF?

In a word, the answer is “compatibility”. This fiber, with a laser bandwidth of 2000 MHz·km @ 850nm complies with the optical fiber performance requirements of the newer laser-based applications. This fiber is also verified to have an LED bandwidth of at least 1500/500 MHz·km, so it can still support all legacy systems using LED sources. Thus, this one fiber type will support the network needs of today (Ethernet, Token Ring, Fibre Channel, FDDI, Fast Ethernet, etc.), of tomorrow (Gigabit Ethernet, 2 Gigabit Fibre Channel, etc.) and beyond (10 Gigabit Ethernet and 10 Gigabit Fibre Channel). Further, this fiber type supports the use of 850nm optical sources – the lowest cost sources – and the electronics that use them (see tables 1 and 2). Now, there is no need to buy higher cost electronics to compensate for lower-performance fiber or to re-cable a facility with single-mode fiber in order to migrate to faster data rates.

The fibers in the XG Fiber System are screened to ensure clean laser light transmission, while still providing clean LED light transmission. Additionally, the fiber performs as a laser certified 50-micron fiber, which means extended distances for Gigabit Ethernet – up to 1000 meters!

Table 1: Distance Capability of Gigabit Ethernet

Table 2: IEEE Distances for 850nm Serial 10 Gigabit Ethernet (10GBASE-SR)

From Table 2, the 10 Gigabit Ethernet distances of 62.5/125µm and 50/125µm at 850nm are too short for a 300m riser distance or for a centralized network. Standard 50/125 optical fiber can support Gigabit Ethernet on a majority of the horizontal, centralized and riser network links installed today, but distance limitations for 10 Gigabit speeds mean either deploying single-mode fibers (and the associated high-cost electronics) to cover a 300m distance or deploying the 850nm laser optimized 50/125µm. The AMP NETCONNECT XG fiber system will support 10 Gigabit applications for TIA-568 horizontal cabling (100 meters maximum), centralized cabling (300 meters maximum) and building backbone cabling (300 meters maximum), as well as short campus backbones to distances of 300 meters. The high data rate capabilities and flexibility of supported applications also make this fiber the recommended fiber type in TIA-942, the standard for data center cabling.

WHY NOT JUST BUY HIGHER BANDWIDTH FIBER?

The bandwidth provided on specification sheets for standard fibers are LED, or overfilled, bandwidth values. For applications where only LED sources will be used, a higher bandwidth may, depending on the application, support higher performance levels. However, LED bandwidth is not a good predictor of performance with laser sources. Because the overfilled measurement minimizes the impact of any index of refraction profile centerline defect, this measurement may not indicate a problem that underfilled launches from laser sources will experience. Accordingly, high LED bandwidth does not mean better laser performance. In fact, some fibers installed today have lower laser bandwidth than LED bandwidth. Another factor to consider is cost. Fiber with higher LED bandwidth is selected from the distribution and carries a cost premium. This may result in a higher priced fiber that will not provide any better laser performance than standard optical fiber. It is also worth pointing out that the Standards do not guarantee any better performance than that shown in Tables 1 and 2 for a higher LED bandwidth. The best way to ensure fiber will support the legacy LED applications of yesterday and today, while supporting the higher data rate laser-based applications of today and tomorrow, is to purchase and install 850nm laser optimized 50/125µm fiber. The fiber bandwidth is certified using a laser measurement test procedure, ensuring its compatibility with VCSEL transceivers, and was designed in cooperation with VCSEL manufacturers to ensure an operational 10Gb/s network.

CONCLUSION

Advances in optical source technology and optical fiber have resulted in higher data rate applications than ever imagined. The fastest short wavelength (850nm) laser-based, enterprise fiber technology today, 10 gigabit, imposes severe limitations on the application of standard 62.5/125 µm fiber, which cannot fully support the requirements of centralized and building backbones. Similarly, while standard 50/125µm fiber can be used for gigabit data rates in horizontal, centralized, and intra-building backbone networks, distance limitations prevent use in maximum length centralized and building backbone links at 10 Gigabit speeds.

The AMP NETCONNECT XG Fiber System provides the best choice for future-proofing the intra-building cabling structure. This new fiber system not only works well with today’s readily available LED-based components, but also provides an effortless migration path into laser-based technology, making it the best choice for applications from 10 Megabits to 10 Gigabits.