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Comparison of OM1, OM2, OM3 & OM4 Multimode Fiber

Multimode and single-mode optical fiber cables are two different cable types in optical networking. Using a larger core size, multimode fiber cable allows multiple light signals to be transmitted in a single fiber over short distances. Multimode fiber systems offer flexible, reliable and cost effective cabling solutions for local area networks (LANs), storage area networks (SANs), central offices and data centers. Unlike the complex classifications of single-mode fiber, multimode fiber is usually divided into four types of OM1, OM2, OM3, OM4. “OM” is abbreviated for optical multimode, and it is specified by the ISO/IEC 11801 international standard. Of course, these four types of multimode fiber have different specifications (as shown in the following table). The article will compare these four kinds of fibers from the side of core size, bandwidth, data rate, distance, color and optical source in details.

specifications-of-multimode-fiber

Core Size

Multimode fiber is provided with the core diameter from 50 µm to 100 µm. Apart from OM1 with a core size of 62.5 µm, other three types are all using the 50 µm. The thick core size makes them able to carry different light waves along numerous paths without modal dispersion limitation. Nevertheless, in the long cable distance, multiple paths of light can cause signal distortion at the receiving end, resulting in an unclear and incomplete data transmission. And this is why all the types of multimode fiber can only be used for short distance.

Bandwidth

Bandwidth is the bit-rate of available or consumed information capacity expressed typically in metric multiples of bits per second. The higher bandwidth is, the faster transmission speed can be. According to overfilled launch (OFL) and effective modal bandwidth (EMB) measurements, OM1 and OM2 can only support OFL, but OM3 and OM4 are able to support both measurements. At the wavelengths of 850/1300 nm under OFL, the respective bandwidth of OM1, OM2, OM3, OM4 is 200/500 MHz*km, 500/500 MHz*km, 1500/500 MHz*km and 3500/500 MHz*km. And at the wavelength of 850 nm under EMB, the bandwidth of OM3 is 2000 MHz*km and OM4 even reaches 4700 MHz*km.

Data Rate

Data rate is a technical term that describes how quickly information can be exchanged between electronic devices. With a higher data rate, the transmission can be more effective. OM1 and OM2 support the Ethernet standards from 100BASE to 10GBASE with a minimum data rate of 100 Mbps and a maximum data rate of 10 Gbps. Compare with OM1 and OM2, OM3 and OM4 are enhanced to support much higher data rates of 40 Gbps and 100Gbps in 40G and 100G Ethernet.

Distance

Multimode fiber is typically used for short distance transmission. But the maximum reaches are varied in different multimode fiber types. Also, on account of different data rates, the transmitting distances are different. However, the common feature is that OM1 always supports the shortest distance yet OM4 supports the longest. For instance, based on the same data rate of 10 Gbps, the maximum reach of OM1 is 33 m, OM2 is 82 m, OM3 is 300 m and OM4 is 550 m. Thus, if a medium-sized transmission is required, OM3 and OM4 are the best choices.

Color & Optical Source

The outer jacket can also be a method to distinguish OM1, OM2 from OM3, OM4. The common jacket color of OM1 and OM2 is orange, and OM3, OM4 are in aqua. In addition, OM1 and OM2 are using a light-emitting diodes (LEDs) optical source but OM3 and OM4 adopt the vertical-cavity surface-emitting laser (VCSELs) optical source.

color-and-optical-source-of-multimode-fiber

Application

OM1 and OM2 are widely employed for short-haul networks, local area networks (LANs) and private networks. OM3 is applied to a larger private networks. Different from the previous multimode types, OM4 is more advanced to be used for high-speed networks in data centers, financial centers and corporate campuses. The video below demonstrated the applications and differences between OM1, OM2, OM3, OM4 and OM5 multimode fibers.

Conclusion

It is very important to choose the right fiber type for your application. Future-proofing network design is crucial for network planning, but there is often a cost for that speed. With a higher performance, OM3 and OM4 are definitely more expensive than OM1 and OM2. So plan well and spend wisely.

Related Article: Applications of Tight-Buffered Distribution Cable
Multimode Fiber Types: OM1 vs OM2 vs OM3 vs OM4 vs OM5

Guide to Multimode Fiber Cabling in 40/100G Migration

Nowadays one and 10 Gbqs data rates are not adequate to meet the continued requirement for expansion and scalability in the data center, thus technology evolves and standards are completed to define higher data rates such as 40/100G Ethernet. In the meanwhile the cabling infrastructures installed today must provide scalability to accommodate the need for more bandwidth in support of future applications. OM3 and OM4 multimode cabling solutions have been proven to be a cost-effective solution for 40G data center. Today’s article will make you familiarize with this new Gigabit Ethernet and OM3/OM4 cabling to help you smoothly upgrade to 40G Ethernet.

Multimode Fibers in Data Center

Multimode fiber is more popular in data centers than singlemode fiber. Many people may know the reason—budget. Because the price of multimode fiber is typically much lower than singlemode fiber. Additionally, multimode fibers utilizes the low cost 850nm optical transceiver for both serial and parallel transmission. While singlemode fiber uses the expensive 1310nm and 1550nm transceiver and duplex fiber wavelength division multiplexing (WDM) serial transmission. Therefore, most data center designers would choose multimode fiber for 40/100G transmission.

OM3 and OM4 cable

There are four common types of multimode fibers available in the market—OM1, OM2, OM3 and OM4. Recently OM3 and OM4 cables are gradually taking place of OM1 and OM2 multimode cable. OM3 and OM4 are laser-optimized multimode fibers with 50/125 core, which are designed to accommodate faster networks such as 10, 40 and 100 Gbps. Compared with OM1 (62.5/125 core) and OM2 (50/125 core), OM3 and OM4 can support high data rate and longer distance. This is why OM3 and OM4 is more popular in data center.

The Ratification of IEEE 802.3ba

The Institute of Electrical and Electronics Engineers (IEEE) 802.3ba 40G/100G Ethernet standard was ratified in June 2010. According to this standard, it includes detailed guidance for 40/100G transmission with multimode and singlemode fibers. But the standard does not have guidance for Category-based unshielded twisted-pair or shielded twisted-pair copper cable.

OM3 and OM4 are the only multimode fibers included in 40/100G standard. Because multimode fiber uses parallel-optics transmission instead of serial transmission due to the 850-nm vertical-cavity surface-emitting laser (VCSEL) modulation limits at the time the guidance was developed. Compared to traditional serial transmission, parallel-optics transmission uses a parallel optical interface where data is simultaneously transmitted and received over multiple fibers. Table 2 shows the IEEE standards for 40 and 100 GbE.

IEEE standards for 40 and 100 GbE

The 40G and 100G Ethernet interfaces are 4x10G channels on four fibers per direction, and 10x10G channels on 10 fibers per direction, respectively. For 40GBASE-SR4 transceivers, it utilizes multimode fiber for a link length of 100m over OM3 and 150m over OM4. QSFP-40G-SR4 is Cisco 40GBASE-SR4 QSFP+ that can both operate over OM3 and OM4 cables to achieve 40G connectivity just as FTL410QE2C.

OM3 or OM4?

As noted before, OM3 and OM4 can meet the requirement for 40G migration cabling performance, that’s why they are being widely utilized in 40/100G migration. But OM3 and OM4, which is better for your infrastructure? There is no exact answer to this question as numerous factors can affect the choice. The working environment and the total costs are always the main factors to be considered when selecting OM3 or OM4 multimode cable.

OM3-and-OM4

OM3 is fully compatible with OM4. They use the same optical connector and termination of connector. The main difference between them is in the construction of fiber cable that makes OM4 cable has better attenuation and can operate higher bandwidth at a longer distance than OM3. On the other hand, 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, in the long term, as the demand increases, the cost will come down. OM4 will become the most viable product in the near future.

Conclusion

No matter choosing OM3 or OM4 for your infrastructure, 40G migration is in the corner. OM3 and OM4 multimode cable featured by the high performance and low cost are the perfect solution for 40/100G migration. Fiberstore is committed to provide the best-service and high-quality products to customers. Our comprehensive range of products in OM3 and OM4 offer customers the ability to create the optimal network. For more information, you are welcome to contact us.

Fiberstore’s 10 Gigabit Ethernet Transceivers and Cables Frequently Asked Questions

What is the difference between SFP+ and SFP?

The pinouts of SFP and SFP+ connectors are identical. However, SFP has a maximum data rate of 5Gb/s whereas SFP+ is designed for 10Gb/s. The SFP receptacles and plugs are not as well impedance matched as SFP+ receptacles and plugs. Also SFP+ cable is designed for 10Gb/s whereas SFP cable may not be able to satisfactorily transmit that rate.

What is the distance supported by the SFP+ SR transceiver?

The supported distance is up to 300 meters depending on the quality of the multimode fiber (MMF) you use. Quality of MMF is listed as OM1 (up to 33 meters), OM2 (up to 82 meters), OM3 (up to 300 meters), and OM4 (up to 400 meters). Check with the supplier for the cable distance supported. Take GP-10GSFP-1S as an example, it is Dell Force10 10GBASE-SR SFP+ covering a distance of 300m over OM3 multimode cable.

Can I use SFP+ cables in SFP ports?

Yes, SFP+ cables are compatible to SFP ports and will work fine. SFP cables are not compatible to SFP+ ports. SFP+ receptacles have a mechanical feature to prevent engaging SFP plugs.

Do Fiberstore’s SFP+ direct-attach Twinx passive cables work with Cisco or other third-party switches?

Fiberstore’s direct-attach SFP+ Twinx passive cables are fully compatible with the original brand like Cisco. For example, SFP-H10GB-CU3M is Cisco SFP+ to SFP+ passive copper cable from Fiberstore which is fully compatible with Cisco switch. The following image shows that our professional trained staff tests the compatibility and interoperability of each optics to make sure our customers to receiver the optics with superior quality.

Fiberstore test program

What are the distances supported by cables to use with the 10GBase-T ports? Does Fiberstore offer these cables?

Data centers have a large installed base of Cat 5/6/7 twisted pair cables for the last decades—initially for 1000BASE-T and now for use with 1/10GBase-T infrastructure. Fiberstore does offer these cables since they are industry standard and widely available from us in various lengths and colors. Distances supported at 10 Gbps speed:

  • CAT 6A and CAT 7 cables supporting 100 meters
  • CAT 5e and CAT 6 cables supporting 55 meters

Do the SFP+ optical transceivers support 1 GbE operation?

Yes, they support 1GbE and 10 GbE dual rates and can be configured for 1 GbE.

Will the SFP+ optical transceivers auto-negotiate between 1 GbE and 10 GbE?

Auto-negotiation is not supported between the 10 GE and 1 GE speed. The transceiver must be manually configured to operate at 1 GE speed.

How do I use the SFP+ ports for 1000BASE-T?

You need to purchase Fiberstore’s SFP+ to 1000BASE-T Media Converter. (SFP+/Copper RJ45), part number FMC-1SFP/1RJ45-GB.

Is TwinX same as Twinax?

Yes.

Does the Twinx copper cable plug directly into the NIC and the switch?

Yes, the copper cable has an SFP+ or QSFP connector on both ends of the cable that directly plugs into the corresponding ports of the switch and NIC.

Should I use optical transceivers with the SFP+ and QSFP direct-attach Twinx copper cables?

No. These are direct-attach Twinx cables and come with connectors that plug directly into the SFP+ port or the QSFP port of the switch/NIC on either end. Transceiver cannot be used.

What is the advantage of SFP+ Twinx copper cable?

It is a low-cost option for shorter distances up to 5 meters.

Is 10GBase-T same as 10GBASE-T?

Yes. 1GBase-T is shorthand for 1000BASE-T and 10GBase-T is same as 10GBASE-T; they are the twisted pair implementations of 1 GbE and 10 GbE respectively.

What are the SFP+ copper cables provided by Fiberstore?

10G SFP+ copper cable

The above chart lists detailed information about some of the 10G SFP+ cables from Fiberstore. We also offer SFP+ copper cables that are fully compatible with major brand like Cisco, Juniper, Brocade, etc. The supported distance of this cable varies from 0.5m to 7m. Users can connect our SFP+ copper cable with top-of-rack (ToR) switch to realize 10G connectivity. For more information, please contact us directly.