Many of us have faced this scenario: you need to plan a new fiber run for your local area network, and the low-voltage contractor asks the critical question:
“Do you want a quote for single-mode or multimode fiber?”
For the contractor, it makes little difference—they’re equally equipped to install either. Both options can meet today’s requirements, so why does the choice matter? The answer lies in one word: longevity.
Let’s rewind to the early 2000s. If faced with the same decision, the choice might have been less clear. At that time, significant cost differences between materials and the necessary optics often led many to choose the more budget-friendly multimode fiber. Fast forward to today, and it’s time to upgrade your network switches. You might be thinking how useful it would be to deploy 25Gbps links to the access layer. However, if you (or a predecessor) opted for 62.5-micron multimode fiber back then, those links would now be limited to just 1Gbps.
On the other hand, had single-mode fiber been installed years ago, it would still support today’s high-speed connectivity requirements as effectively as a brand-new installation. Two decades ago, future-proofing with single-mode fiber came at a steep price. But today, the cost difference between single-mode and multimode fiber is negligible. For typical speeds between distribution and access-layer switches, even the price gap for optics has largely disappeared.
That said, multimode fiber and optics still have a place in enterprise networks. As we focus on higher-link speeds, the cost difference between multimode and single-mode optics becomes more pronounced. For example, 40Gbps, 100Gbps, or even 400Gbps interconnects—commonly used between redundant core switches or in leaf-spine architectures—make a compelling case for multimode. When the only sunk cost involved is for the patch cable, choosing multimode in these scenarios is often the more economical option. For enterprise data centers, a balanced approach is often best: use a mix of single-mode and multimode fiber for cabinet-to-cabinet connectivity.
A General Guideline
- Within a single room: Multimode fiber is typically the more cost-effective choice.
- Between rooms: Always request single-mode fiber.
Twenty years ago, we couldn’t predict that future optical data rate standards would continue to favor OS2 single-mode fiber. Today, however, hyperscale data centers give us a clear advantage: we know that when the time comes to push 800Gbps to the access layer, standards and optics are already available to support it—using the same single-mode cabling you have installed today.
