Two Core Sizes of Multimode Fiber Optic Cable

Fiber jumpers continue to provide a cost-effective cabling solution for data centers, local area networks (LANs), and other enterprise applications. Singlemode fiber optic patch cords and multimode fiber optic patch cords are two options. Compared to singlemode fiber, multimode fiber has a large diameter core, which allows multiple wavelengths of light traveling in the fiber core at the same time. Multimode fiber optic patch cord comes with two core sizes: 50 micron and 62.5 micron. And this article will talk about these two core sizes of multimode fiber optic cables.

Overview

The numbers 50µm and 62.5µm refer to the diameters of the glass or plastic core, the part of the fiber that carries the light which encodes your data. The dimensions are sometimes specified as 50/125μm and 62.5/125μm, to include the diameter of the cladding, which confines the light to the core because it has a lower index of refraction. You can use both in the same types of networks, although 50µm cable is recommended for premise applications, like backbone, horizontal, and intrabuilding connections. They both can use either LED or laser light sources. The main difference between 50µm and 62.5µm cable is in bandwidth, 50µm cable features three times the bandwidth of standard 62.5µm cable, particularly at 850nm. The 850nm wavelength is becoming more important as lasers are being used more frequently as a light source. Other differences are distance and speed. 50µm cable provides longer link lengths and higher speeds in the 850nm wavelength.

62.5µm Multimode Fiber Optic Patch Cords

OM1 fiber optic cable is the 62.5/125 multimode fiber cable. OM1 fiber has a bigger core diameter, which makes it better at concentrating the light and bend-resistance. OM1 fiber was the indoor cabling standard chosen by AT&T, ANSI and IBM. For OM1 fiber cable, the max attenuation is 3.5dB/km working at 850nm, 1.5dB/km at 1300nm. Overfilled launch of OM1 fiber optic cable at 850nm is 200MHz*km, at 1300nm is 500MHz*km. Today, OM1 fiber optic cables are still a popular indoor use multimode fiber optic cable.

50µm Multimode Fiber Optic Patch Cords

50µm fiber includes OM2, OM3, OM4. OM2 fiber optic cable refer to the commonly used 50/125 traditional multimode fiber cable. OM1 and OM2 are both orange jacketed cable, and you cannot judge from the outer diameter to identify OM1 and OM2 fiber cable, because the 50/125 and 62.5/125 refer not to whole cable diameter but to the fiber inside. OM2 multimode fiber cables are used in fiber optic telecommunications and high speed transmission systems that require simultaneous, bi-directional data transfer.

OM3 cable and OM4 cable are both optimized for laser based equipment that uses fewer modes of light. As a result of this optimization, they are capable of running 10 Gigabit Ethernet at lengths up to 300m and 550m respectively. OM4 is completely backwards compatible with OM3 fiber and shares the same distinctive aqua jacket. OM4 was developed specifically for VSCEL laser transmission. OM4 multimode fiber optic cable is the highest level of multimode fiber optic cable that you can use. They can be used in networks where an overwhelming or extreme amount of data transfers will take place.

Which One Should You Choose?

Given its superior technical characteristics for high-speed links, 50μm fiber is the clear choice for new multimode fiber links in most circumstances. OM3-grade, high-bandwidth 50/125-micron fiber cable increases the flexibility of network designs and achieves data transfer rates up to 10Gbps at the lowest available cost. 50μm multimode fiber is the medium of the future, with 62.5μm fiber being supported chiefly for legacy purposes. However, the majority of the fiber deployed in the world today is 62.5μm, so backward compatibility is an important concern. On the other hand, there are no technical drawbacks to using different fiber types in separate network links, as long as the ports at both ends of the link are compatible with the cable. In a word, installing 50μm fiber for new network links is a good investment for future growth.

Summary

With the increasing demand for network capacity, upgrades must be planned with an eye to the future. Installing 50μm multimode fiber today brings immediate benefits of longer cable reach and improved light loss budget margins, and prepares the network for future upgrades.

Migrating to 40/100G Era with OM3 and OM4

To meet the continuously increased requirements, data center 40/100G migration is underway. The infrastructure of data centers for the 40G/100G should meet the requirements like high speed, reliability, manageability and flexibility. Fiber optic patch cable plays an important part. The cable used in data center must be selected to provide support for the higher needs of data rate. OM3 and OM4 fiber patch cables have gradually become the popular choice of data center during 40/100G migration. This article illustrates OM3/OM4 multimode fiber cables in 40/100G migration in details.

Why Choose OM3 and OM4 in 40/100G Migration?

OM stands for optical multimode. Why not single-mode fiber cables? The answer is the cost. The price of single-mode fiber is generally more expensive than multimode fiber. Multimode fiber utilizes low cost 850nm transceivers for serial and parallel transmission. Why not OM1 or OM2? Compared with OM1 and OM2, OM3 and OM4 can transport data at higher rate and longer distance. OM3 and OM4 are both laser-optimized multimode fibers with 50/125 core, which are designed for use with 850nm vertical-cavity surface-emitting laser (VCSEL) and are developed to accommodate faster networks such as 10, 40 and 100 Gbps. The IEEE 802.3ba 40/100G Ethernet Standard provides specific guidance for 40/100G transmission with multimode and single-mode fibers. OM3 and OM4 are the only multimode fibers included in the standard. The reason why OM3 and OM4 are applied in 40/100G migration is that they can meet the requirements for the migration cabling performance.

Advantages of Utilizing OM3 and OM4

Bandwidth, transmission distance and total connector insertion loss are three main factors should be considered when evaluation the performance needed for cabling infrastructure to meet the requirements for 40/100G. Advantages of utilizing OM3 and OM4 in these three aspects will be explained below.

Higher Bandwidth: OM3 and OM4 are optimized for 850nm transmission and have a minimum 2000MHz∙km and 4700MHz∙km effective modal bandwidth (EMB). Comparing the OM1 and OM2 with a maximum of 500 MHz∙km, advantages of OM3 and OM4 are obvious.

Longer Transmission Distance: OM3 fiber and OM4 fiber can support longer transmission distance compare with other traditional multimode fibers. Generally OM3 fibers can run 40/100 Gigabit at 100 meters and OM4 fibers can run 40/100 Gigabit at 150 meters. This high data rate and longer distance cannot be achieved by other traditional multimode fiber like OM1 and OM2.

Lower Insertion Loss: According to the 40/100G standard, OM3 fiber is specified to a 100m distance with a maximum channel loss of 1.9dB, which includes a 1.5dB total connector loss budget. And OM4 fiber is specified to a 150m distance with a maximum channel loss of 1.5 dB, including a total connector loss budget of 1.0 dB. With low-loss OM3 and OM4 fiber, maximum flexibility can be achieved with the ability to introduce multiple connector mating into the connectivity link and longer supportable transmission distance can be reached.

OM3 or OM4?

OM3 and OM4 are both available for 40/100G applications. But you also need to choose which one to use. The applications and the total costs are always the main factors to consider to figure out whether OM3 or OM4 is needed. The connectors and the termination of the connectors for OM3 and OM4 fibers are the same. OM3 is fully compatible with OM4. The difference is just in the construction of fiber cable, which makes OM4 cable has better attenuation and can operate higher bandwidth at a longer distance than OM3. Thus, the cost for OM4 fiber is higher than OM3. As 90 percent of all data centers have their runs under 100 meters, choosing OM3 comes down to a costing issue. However, looking in the future, as the demand increases, the cost will come down. Thus, OM4 might be the most viable product at some point soon.

Conclusion

Migration to 40/100G has already been underway. With good performance like high data rate, long transmission distance and lower inserting loss, it seems that OM3/OM4 fiber cable is a must in data center migration to 40/100G.