OM3 And OM4 Fiber for 10G/40G/100G Network

Multimode fiber has been highly favored by Ethernet users and gained the widest acceptance in network backbones where it has offered users the opportunity to extend link distances, increase network reliability, and lower costs by centralizing electronics. OM3 fiber emerges just at the right time. The predominance of OM3 fiber is that utilizes laser-optimized fiber, which is the highest-capacity medium for short-wave 10G optical transmission. OM4 fiber just joined multimode fiber family after OM3 fiber in order to meet the requirement of longer range applications. This passage would give a brief introduction to OM3 and OM4 fiber, give a further analysis on their differences and selection guide, as well as list their applications.

Introduction to OM3 & OM4 Fiber

Both OM3 and OM4 fiber meet the ISO 11801 standard. The standard specifies that OM3 fibers are capable of 10 Gb/s performance over distances of up to 300m. Like being mentioned, the laser optimized 50/125 mm multimode OM3 fiber is of predominance, which provides sufficient bandwidth to support 10 GbE and beyond with cable lengths up to 550 meters. OM4 fiber is a further improvement to OM3 fiber. It also uses a 50µm core but it supports 10 Gigabit Ethernet at lengths up 550 meters and it supports 100 Gigabit Ethernet at lengths up to 150 meters.

OM4 fiber cable

Main Difference Between OM3 And OM4 Fiber

—Optical attenuation

Attenuation is caused by losses in light through the passive components, such as cables, cable splices, and connectors. Attenuation is the reduction in power of the light signal as it is transmitted (dB). The maximum attenuation of OM3 and OM4 fiber allowed at 850nm: OM3<3.5 dB/Km; OM4 <3.0 dB/Km. So it is obvious that OM4 fiber causes lower losses due to different construction.

—Modal dispersion

As is known to most people, modal dispersion attaches great importance to bandwidth. The lower the modal dispersion, the higher the modal bandwidth and the greater the amount of information that can be transmitted. The minimum OM3 and OM4 fiber cable bandwidth at 850nm: OM3 2000 MHz·km; OM4 4700 MHz· km. The higher bandwidth available in OM4 means a smaller modal dispersion and thus allows the cable links to be longer or allows for higher losses through more mated connectors.

OM3 And OM4 Fiber 10G/40G/100G Transmission Distance

The maximum transmission distance of OM4 fiber is 400-550m (depending on module capability) while OM3 fiber can only be up to 300m. And thus, OM4 can tolerate a higher level of loss at distances between 200-300m as it is designed to operate at longer distances than OM3 fiber. It may be a more flexible option for network managers to install OM4 fiber within these instances. You can check difference between OM3 and OM4 in transmission distance in the following table.

OM3 and OM4 fiber cable distance

OM3 And OM4 Fiber Price

In comparison to OM3 fiber, the cost for OM4 is higher due to the manufacture process and market fluctuations. In a large extent, cost depends on the construction type of the cable (loose tube, tight buffered, etc.). OM4 fiber cable is about twice as expensive as OM3 fiber cable. This means that the cost difference of lots of fiber products such as standard fiber patch panels, MTP cassette modules, fiber patch cords is very small (as the volume of cable is small).

OM3 And OM4 Fiber Selection Guide

Fifty micron OM3 fiber is designed to accommodate 10 Gigabit Ethernet up to 300 meters, and OM4 can accommodate it up to 550 meters. Therefore, many users are now choosing OM3 and OM4 over the other glass types. In fact, nearly 80% of 50 micron fiber sold is OM3 or OM4. If you require higher data rates or plan on upgrading your network in the near future, laser optimized 50 micron (OM3 or OM4) would be the logical choice. Compared to OM4, OM3 fiber is more future proofing for most applications, which allows speeds of 10 GB/s up to 100 GB/s. OM4 fiber provides users a transmission solution over longer distances and leaves more wiggle room in optical budgets.

OM3 and OM4 fiber cables are typically used in data center structured cabling environments running high speeds of 10G or even 40 or 100 Gigabit Ethernet, SAN (Storage Area Networking), Fiber Channel, FCOE (Fiber Channel Over Ethernet) with such manufacturers as Cisco, Brocade, EMC and others. Typical applications could be virtualized or internal cloud core data center applications. For 40G and 100G fiber cable applications, MTP/MPO cable would also be a great choice. MTP cabling assemblies (MTP/MPO trunk cable, MTP/MPO harness cable, MTP/MPO conversion cable, etc), with their overwhelming advantages, providing a fast, simple and economical upgrade path from 10 Gigabit to 40 or 100 Gigabit applications.

Conclusion

In this article, we mainly discussed OM3 fiber, OM4 fiber, their main differences, transmission guide and applications for 10G/40G/100G network. We put emphasis on OM3 and OM4 fiber 10G/40G/100G transmission distance and selection guide. OM3 and OM4 multimode fiber provide a cost effective solution for inside buildings or corporate campuses. Hope this article would be helpful for you to understand OM3 and OM4 fiber and to select right fiber cable for yourself.

Next-Generation OM3 Multimode Fiber

We know that conventional datacom links use single-mode fiber (SMF) for long-distance, high-speed links and multimode fiber (MMF) for shorter links. Early datacom applications, including ESCON, Token Ring, FDDI, Ethernet, and ATM, operated at relatively slow data rates (4-155 Mbit/s), using low-cost infrared light-emitting diode transmitters (LEDs). And this article will focus on OM3 multimode fiber.

The Development of MMF

The earliest fibers, called Optical Multimode 1 (OM1), featured a large core than is used today and a bigger numercial aperture. As the technology matured, smaller core MMF was typically rated for a minimum bandwidth-distance product around 160 MHz*km for 62.5/125 micron fiber at 850 nm wavelength; 500 MHz*km for 50/125 micron fiber at this wavelength; and 500 MHz*km for both fiber types at 1300 nm wavelength. This fiber was compatible with various industry standards, including CCTIT recommendation G.652, and was defined by the ISO standards as “optical multimode2” (OM2) fiber; it is also commonl known as “FDDI grade” fiber, The fiber bandwidth was measured using an overfilled launch (OFL) test procedure, which replicated the large spot size and uniform power proflle of an LED. Since an LED consistently fills the entire fiber core, the fiber bandwidth is determined by the aggregate performance of all the excited modes. However, LED sources typically have a maximum modulation rate of a few hundred Mbit/s; with the growing demand for higher data rates, laser sources operating over SMF were required.

Issues Related to VCSELs

Single-mode links using Fabry-Perot or distributed feedback lasers operating at long wavelength (1300nm) tend to be higher cost due to their tighter alignment tolerances and higher performance characteristics. There is lower cost alternative; the recent deployment of short-wave (780-850 nm) vertical cavity surface emitting lasers (VCSELs) has made it possible to use MMF at higher data rates over longer distance. Compared with LEDs, VCSELs offer higher optical power, narrower width, smaller spot size, less uniform power profiles, and higher modulation data rates. This means that a VCSELs will not excite all of the modes in a MMF; the fiber bandwidth is determined by a restricted set of modes, typically concentrated near the center of the core. Older MMFs experienced significant, often unpredictable variations in bandwidth when used with VCSEL sources due to defects or refractive index variations in the fiber core and variations in the number and power of excited modes due to fluctuations in the VCSEL output or between different VCSEL transmitters.

In response to these problem, the datacom industry developed a new type of laser-optimized or laser-enhanced MMF specifically designed to achieve improved, more reliable performan with VCESLs. Precise control of the refractive index profile minimizes modal dispersion and differential mode delay (DMD) with laser sources, while remaining backward compatible with LED sources (the dimensions, attenuation, and termination methods for laser-optimized and conventional fiber are the same). The first laser-optimized fibers, introduced in the mid-1990s, were available in both 50-microns and 62.5-micron varieties and designed for 1-Gbit/s operation up to a few hundred meters. These fibers were not always capable of scaling to higher data rates; with the increased attention on 10-Gbit/s links, never types of reaching about 35 meters at 10-Gbit/s, it became apprarent that the samller core diameter and reduced number of modes in 50 micron fiber made it the preferred choice for these data rates. Today, laser-optimized fiber is commonly available only in 50-micron versions, with an effective bandwidth-distance product around 2000 MHz*km for 850 nm laser sources. The bandwidth must be measured using a restricted mode launch (RML) test, instead of the conventional OFL method. This fiber was defined in the TLA-568 standard as “laser-optimized multimode fiber, ” and in the ISO 11801 (2nd edition) by its more common name, “optical multimode3” (OM3) fiber. Click to buy OM3 fiber patch cables.

Colors of Fiber Cables

An early example of laser-optimized fiber is the Systimax Lazer SPEED fiber introduced by Lucent, which uses a green jacket to distinguish it from existing multimode (orange) , single-mode (yellow) , and dispersion-managed (purple) fiber cables. Attenuation is about 3.5 dB/km at 850 nm and 1.5 dB/km at 1300 nm; bandwidth is 2200 MHz*km at 850 nm (500 MHz*km overfilled) and 500 MHz*km at 1300 nm (no change when overfilled) . Another example is the Corning Infini-Core fiber, which typically uses an aqua-colored cable; the CL 1000 line consists of 62.5-micron fiber made with an outside vapor deposition process that achieves 500-m distances at 850 nm and 1 km at 1300 nm. Similarly, the CL 2000 line of 50-micron fiber supports 600-m distances at 850 nm and 2 km at 1300 nm. Here is a figure of OM3 multimode fiber for you.

OM3 multimode fiber

Applications of OM3

Most recent installations of Ethernet, Fibre Channel, InifiniBand, and other systems use the preferred OM3 multimode fiber (for example, the OM3 SC to LC), and many legacy systems including ESCON are compatible with this fiber. In order to avoid the associated with installing new fiber, most standards attempt to accommodate various types of MMF. While the idea of backward compatibility works reasonably well up to 1 Gbit/s (distances of a few hundred meters can be achieved) , it begins to break down at higher data rates when the achievable distance is reduced even further. Designing a future-proof cable infrastructure under these conditions becomes increasingly difficult; at some point, new fiber needs to replace the legacy MMF. Although SMF should be a good long-term investment, the short-term cost premium for SMF installation and ports on many switches, servers, and storage devices remains a concern. Since the cost of short-wave transceivers is presently lower than long-wave transceivers, there is still some question as to the preferred fiber to install and the best mixture of 62.5-micron and 50-micron MMF. In general, 50-micron fiber has been widely deployed in Europe and Japen, while North America has primarily used 62.5-micron MMF until recently. The IEEE has recommended using 62.5-micron MMF in building backbones for distances up to 100m, and 50-micron fiber for distances between 100 and 300 m.

Conclusion

Mixing OM2 and OM3 fibers in the same link results in an aggregate bandwidth proportional to the weighted average of the two cabletypes. Care must be taken not to mix 50-and 62.5-micron fibers in the same cable plant, as the resulting mismatch in core size and numerical aperture creates high losses. This can make it difficult to administer a mixed cable plant, as there is no industry standard connector keying to prevent misplugging different types of MMF into the wrong location.

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