In this episode JT explains some of the physical and application differences between multi-mode and single-mode fiber optic cables. Multi-mode is typically used in data centers. At this time it should be OM3 or OM4. Single-mode is used in "long haul" applications due to the higher cost of the active electronics.



Hi, I'm Josh Taylor, product manager with CABLExpress.

Today, we're going to talk about the differences between multi-mode and single-mode fiber. First, let's talk about the physical differences.

 Single-mode almost always has a yellow jacket, especially when used inside a building. Multi-mode traditionally has an orange jacket. More recently, it has an aqua jacket. There are currently 4.

Let's talk about core sizes. That's where the actual data is transmitted over the core. Single-mode has a much smaller core than multi-mode. See video #8 for a lot more information on multi-mode and single-mode core sizes.

Let's talk about application differences. Using the larger core size of multi-mode fiber allows for the use of VCSELs, or vertical cavity surface emitting laser. This, compared to a higher cost laser used in single-mode transceivers.

A good analogy here is a flashlight for multi-mode, and a laser pen for single-mode. For short distances, the broad beam of a flashlight is perfect, but if you need to reach out a long distance, the concentrated beam of the laser pen will go much further.

Cost is almost always an issue. If cost weren't an issue, everybody would use single-mode, and then your only problem would be, "is my signal too strong?"

The fact is that single-mode channels cost an average of 4X more than multi-mode channels, and that includes the electronics that drive the data. That's the reason why most data-setters use a multi-mode fiber optic infrastructure.

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