OM Cables: Essential pieces of equipment in Telecom

When dealing with Fiber Optics cables, the plethora of available options can certainly be overwhelming. There are just so many types of cables that one could get lost amongst that vast diversity.

Nonetheless, many Telecom experts and enthusiasts agree on the fact that once you’re able to have a solid understanding on the particularity of every type of cable, then that diversity doesn’t look intimidating anymore -it looks enriching instead.

Broadly speaking, Fiber Optic cables can be divided into two main types: Multimode fiber (OM) and Single Mode (SM) fiber cables. The vast majority of cables available out there fit into one of these two categories, which are often referred to cable transmission performance.

Differences between OM and OS cables

OM and OS cables are mainly distinct from their size of core. Multimode fibers typically have a much larger core size, in contrast to single mode’s core of 8 to 10 microns. This expansion in space enables this type of cable to accommodate multiple fibers into one cable, hence their title.



OM’s larger core enables it to handle more light compared to single mode, and thus allows a larger quantity of signals to be transmitted. Consequently, this transmission of several modes of light can provoke signals to lose their potency over time and therefore travel shorter distances.

The most common core sizes in OM cables are 50 micron and 62.5 micron. Both 62.5 microns and 50 microns patch cable have the same glass cladding diameter of 125 microns. These lengths should be specified in the labeling of these cables when you get to purchase them. And if they’re not visible, then you should ask the manufacturer.

OM’s larger core size facilitates multiple connections and it also enables the use of light sources that operate at 850 nm and 1300 nm. In contrast, OS cables usually operate at 1310 or 1550 nm wavelengths, which calls for more expensive light sources.

OM cables tend to have lower bandwidth distances, compared to OS’, because their larger core sizes can handle multiple propagation modes. This makes OM cables limited by modal dispersion.

Another limitation of OM cables is represented by the chromatic dispersion originated by the range of wavelengths that are transmitted at different speeds. In this regard, OS cables the type of light they transmit is slightly more coherent due to the narrowness of the wavelength. 

Differences between different types of OM cables


OM1 cables have a larger core diameter. This makes them better choices for concentration of light and bend-resistance. Nowadays, OM1 cables remain the preferred choice for indoor applications, in spite of presenting limitations for demands in high speed. 

OM2 cables have a core of 50 microns. These cables are often employed in Telecom applications and high speed transmission systems that demand simultaneous and bi-directional data transfers.



OM3 cables have a core of 50 microns, but it has been optimized for laser based equipment that employs fewer modes of light. Because of this upgrade, OM3 cables are able to transmit 10 Gigabit Ethernet at lengths up to 300 meters.

OM4 cables are 50µm laser-optimized cables that feature extended bandwidths. It is mainly employed in networks that call for extreme amounts of data that need to be transmitted. Both OM4 and OM3 cables feature their highly distinctive aqua jacket.

OM4 cables constitute the go-to choice for modern standards that operate at 40Gb and even 100Gb up to 150m, and these cables are also very popular in Data center applications.

OM Cables’ Evolution

OM1 and OM2 cables were often the most popular cables amongst premises applications throughout the last couple of decades. Their properties and qualities made them an ideal fit for support applications such as Ethernet both in the Mega and Gigabits rates of transmission.


As transmission rates increased, the shift from OM1 and OM2 to OM3 and OM4 was inevitable, since the latter were the ones that were able to handle such rapid transmissions.



Another factor to take into account regarding multimode fiber cables is “modal bandwidth”. Since OM1 and OM2, for example, function with light sources that surpass the numerical aperture of the fiber, their modal bandwidth values are referred to as “overfilled launch”.

On the other hand, OM3 and OM4 call for restricted launch conditions so they’re able to manage high modal bandwidths besides the “overfilled” launch.

OM cables in general represent a great solution for the transmission of signals that carry data and voice signals over short distances. The differences between multi-mode cables dictate their use in specific and particular applications.

Having a solid knowledge both on what your installation and project may need, and the types of cables previously described, will lead to proper match between the problem and its potential solution.

At Beyondtech, we offer many options of multi-mode cables that can satisfy your requirements. If you need any of these cables, please let us know and contact us. We’d be happy to help!

June 30, 2021 by Luis Cardenas
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