There’s a multitude of decisions to make when setting up a fiber network. One of the first is whether to use single or multimode fiber, which may be confusing as each has unique advantages and disadvantages.
Knowing the differences could help maximize your fiber optic network performance and avoid problems in the future.
To decide between single vs. multimode fiber for your project, let’s take a closer look at the options.
Construction
Single mode and multimode fibers are physically different. The single mode has a smaller core size, with a typical diameter of around 10µm. A multimode fiber core is either 62.5µm or 50µm, a difference that is impossible to see with the naked eye.
With protective cladding, both single and multimode fibers have a diameter of 125µm.
Functionality
“Single mode” or “multimode” describes a fiber’s light-carrying capability. Only one mode of light can pass through a single-mode fiber, while a multimode fiber can transmit several modes of light simultaneously.
How does this impact functionality?
As light travels down a single mode fiber, its narrow core size restricts reflection, making it possible for a signal to travel long distances without distortion.
Compared to single mode fiber, multimode has superior light-gathering capability. As more data can pass through the fiber’s core, multimode works with a broader range of electro-optic devices.
Making Your Choice: Single Mode or Multimode Fiber
After learning the distinctions between single vs. multimode fibers, it’s easier to decide which is best for your project. Taking the following considerations into account will help.
Distance
Single mode fiber is not limited by distance—meaning it can carry a signal for miles. On the contrary, multimode fiber is better used to a maximum length that’s far less than one mile.
Here’s why this is important when you’re choosing between single vs. multimode fiber.
The distance that a multimode fiber can be used depends on a network’s optical power budget and fiber bandwidth. The first of the two, power budget or bandwidth, to reach its limit determines a network’s maximum range.
Applications with low bandwidth and low data rates (ex. analog video) are typically restricted by their optical power budget.
At the other end of the spectrum are applications with high bandwidth and high data rates. Modal dispersion is the phenomenon that constrains these types of networks.
Modal dispersion
In a multimode fiber, a signal disperses or spreads the farther it travels. This “modal dispersion” limits the information-carrying capability and is directly related to fiber length—the longer the fiber, the greater the dispersion.
As previously mentioned, multimode fiber comes in two core sizes: 62.5µm or 50µm. A smaller fiber core allows less dispersion, so a 50µm fiber permits a greater network range than a 62.5µm fiber.
But here’s the interesting part. Since it’s easier to inject optical energy into a 62.5µm fiber, a network may be better off using a multimode fiber with a larger core despite its greater modal dispersion.
Cost
Fiber optic network cost depends on design—a skilled network architect has the knowledge to help determine your optical requirements. With their professional advice, you can better start to factor cost into your decisions.
For example, single mode fiber costs less than multimode fiber. But single mode transceivers and components are more expensive and more challenging to install than multimode.
When considering whether to choose single vs. multimode fiber, it’s important to take system functionality into account, as well as the cost of individual network components. In some cases, better functionality may outweigh the cost.
Future Upgrades
Most people can’t see the future, but that doesn’t mean you can’t anticipate it. Will there be an expansion to remote locations? Are data needs likely to increase? Do you need backward compatibility with an existing network?
Asking questions like these can help decide whether single or multimode fiber is best for your project in the long run.
Different Fibers for Different Applications
Here are a few last-minute points to keep in mind when choosing between single and multimode fiber.
Multimode works well for:
- LANs
- Offices
- Businesses
Single mode works well for:
- Undersea applications
- Connecting remote offices
- College & university campuses
And a final word of caution: single and multimode fibers are not compatible—you must choose one or the other to connect two points.
Connect with ComNet’s Fiber Experts
At ComNet, we offer our customers superior, one-on-one technical phone support. Call our experienced fiber optic team to help determine the right fiber optic products to make your project a success.