OM3 vs OM4 Multimode Fiber: Which to Choose

Fiber optic cables consist of single-mode fiber and multimode fiber. In the previous post, we discussed the differences between single-mode fiber OS1 and OS2. How about the multimode fiber? Multimode fiber also includes many types, including OM1, OM2, OM3, OM4, and OM5. Among them, OM3 and OM4 multimode fibers are the most widely used types today. The following post will discuss the differences between OM3 and OM4 fiber, and how to choose between them.

OM3 and OM4 Explained

OM3: A1a.2 fiber defined by IEC 60793-20. Designed for short-range transmission at 10Gps speed, such as 10 gigabit transmission in buildings.50/125μm structure, with 50μm fiber core and 125μm cladding. Compared to its previous version of OM2 fiber, OM3 uses an optimized VCSEL laser, providing higher transmission bandwidth at an 850nm transmission window. OM3 supports 10GBASE-SR at 300 meters, 40GBASE-SR4 at 100 meters, and 100GBASE-SR4 at 70 meters.

Besides the 10GBASE-SR and 40G/100GBASE-SR4, OM3 fibre also support the following transmission applications:
100BASE-FX
100Mbit/s Token Ring
1000BASE-SX
1000BASE-LX
10GBASE-LX4 
1Gbit/s Fiber Channel
2Gbit/s Fiber Channel
4Gbit/s Fiber Channel
8Gbit/s Fiber Channel
16Gbit/s Fiber Channel

OM4: A1a.3 fiber defined by IEC 60793-20. Designed for short-range transmission at high-speed transmission data rates of 40G/100G. Same as OM3 fiber, OM4 also uses a 50/125μm structure and optimized laser. The supported transmission bandwidth is higher than OM3. OM3 supports 10GBASE-SR at 400~550 meters, 40GBASE-SR4 at 150 meters, and 100GBASE-SR4 at 100 meters.

Besides the 10GBASE-SR and 40G/100GBASE-SR4, OM4 fiber also supports the following transmission applications:
100BASE-FX
100Mbit/s Token Ring
1000BASE-SX
1000BASE-LX
10GBASE-LX4
1Gbit/s Fiber Channel
2Gbit/s Fiber Channel
4Gbit/s Fiber Channel
8Gbit/s Fiber Channel
16Gbit/s Fiber Channel
32Gbit/s Fiber Channel

OM3 vs OM4, What Are the Differences?

Distance: When working on the same devices, no matter 10Gb, 40Gb, or 100Gb, the max distance of OM4 is longer than OM3. 
For 10Gb transmission over 10GBASE-SR transceivers, OM3 supports only 400 meters while OM4 allows at least 400 meters, which is set by TIA and IEEE spec standards based on the worst scenario. The 10Gb OM4 max distance can even up to 550 meters when working on some high-performance Ethernet switches. 
For 40Gb transmission over 40GBASE-SR4 transceivers, OM3 enables 100 meters while OM4 supports max distance up to 150 meters. The OM4 distance increased by 50% compared with OM3.
For 100Gb transmission over 100GBASE-SR4 transceivers, OM3 supports a link length up to 70 meters, while OM3 supports an extended distance of 100 meters.

Speed: As mentioned above, since OM4 supported transmission distance is longer than OM3, If you are building a 40G/100G network, OM4 fiber will be a better choice. And OM3 is more suitable for 10Gb applications. 

Bandwidth: The most important specification that distinguishes OM3 from OM4 is the modal bandwidth on 850nm. The minimum effective modal bandwidth (EMB) measures the multimode fiber's ability to minimize its distortion as the optical signal is transmitted through the fiber. The higher the EMB value, the lower the optical distortion. OM3 and OM4 fiber have a minimum of EMB of 2000 MHz*km and 4700 MHz*km EMB respectively. That's why OM4 has a better performance than OM3.

Attenuation: The attenuation of OM4 fiber is lower than OM3. At 850nm, the max attenuation of OM4 is 3.0 dB/km, while the OM3 is 3.5 dB/km.

Cable Color: It is difficult to distinguish each cable type in a data center since there are always various types of cables, so international standard defines different fiber cable jacked color to help distinguish different fiber optic cable types. For indoor non-military applications cable, the color of OM1 and OM2 fiber cable is orange. Firstly, both the OM3 and OM4 fiber use aqua, which caused difficulty in distinguishing them from each other, especially when staring at the front of a panel where all the adapters look the same. To solve this problem, in the Europe market, OM4 fiber cables use violet color as distinct from the OM3 fiber cables. Eventually, the new violet color of OM4 is now widely used. 

Price: The OM4 price is a litter bit higher than OM3 since it has better performance, however, their price difference is so slight that it can be ignored due to the improved manufacturing technology.

We Pick OM4 as the Better Choice

Both OM3 and OM4 support 10G, 40G, and 100G transmission, considering the OM4 allows longer transmission distance and better transmission performance than OM3, and their price difference is very slight, OM4 might be the better choice for network cabling deployment. QSFPTEK provides OM3 and OM4 fiber cables at very reasonable prices, a 2-meter LC-LC OM3 cable costs $3.6, and a 2-meter LC-LC OM4 cable costs $4. SC, MTP/MPO connector types are also available. Welcome to consult via sales@qsfptek.com.