Multimode Fiber – OM1 to OM5 (Characteristics and impact on bandwidth)

Once you have decided that the fiber you will use will be of the Multimode type (MM or MMF), you will come across another technical specification that you need to know: what type of multimode fiber should I use? OM1, OM2, OM3, OM4 or OM5?

I will talk about the types of multimode fiber available on the market, their characteristics and which one is recommended for each case.

What is Multimode fiber?

Multimode fiber is the most common type of fiber to be used for connections over short distances, such as in the same room, the same building or even neighboring buildings. Although the cable is very similar to single-mode fiber, the fiber core is larger (50 or 62.5 microns) which allows multiple types of signals to be propagated through the fiber.

The maximum transmission distance through multimode fiber is up to 2km, which may vary according to the type of transmission (100Mbps, 1000BASE, 10GBASE, 40GBASE, 100GBASE, etc.), frequency and other factors.

Types of Multimode Fiber

When we choose which type of multimode fiber will be used, we need to ask 3 questions to define the best option:

• How long fiber will be needed?
• What will be the bandwidth transmitted by the fiber?
• What to expect from this fiber in the long term? That you are prepared for future technologies?

I prepared a table with the main data on multimode fibers of the types OM1, OM2, OM3, OM4 and OM5.

The use of fiber types OM1 and OM2 no longer makes sense, as they have a very poor performance compared to the others and without much benefit in relation to costs.

The best options for building a multimode fiber network or link are OM3 and OM4, which have the best cost-benefit ratio among the others. The difference between OM3 and OM4 fiber is only in the construction of the fiber optic cable. The difference in construction means that OM4 cable has better attenuation and can operate at greater bandwidth than OM3.

Multimode cables are available in different colors so they can be easily recognized. 

OM1 (62.5/125):

OM1 optical fibers are typically characterized by an orange jacket, but the individual fibers within the cable may follow the common color-coding scheme mentioned earlier (e.g., blue, orange, green, etc.).OM2 (50/125):

OM2 optical fibers are also often associated with an orange jacket, but, like OM1, they can follow the same color-coding scheme for individual fibers.OM3 (50/125):

OM3 optical fibers are sometimes identified with an aqua-colored jacket. The individual fibers within the cable may still adhere to the standard color-coding scheme.OM4 (50/125):

OM4 optical fibers may also have an aqua-colored jacket in some cases. Individual fiber colors can vary by manufacturer.OM5 (50/125):

OM5 optical fibers are typically associated with a lime green or lime green/aqua dual-color jacket, distinguishing them from OM3 and OM4 fibers.Remember that while these colors are commonly used to identify the jacket of fiber optic cables with these fiber types, variations in jacket color may exist depending on the manufacturer and specific product. The critical information for identifying the fiber type is the OM designation (e.g., OM1, OM2, etc.) and the core/cladding size (e.g., 62.5/125 or 50/125), as this specifies the fiber’s optical performance characteristics.

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