Smart Buildings

Singlemode or Multimode Fiber: Demystifying the Differences

Michael Houck

Until recently, copper cabling systems—including twisted-pair Category or Ethernet cables and hardware devices like switches and routers—have been the go-to way to distribute data throughout a business.


While they’ve fulfilled their purpose for years, it’s no secret that copper cabling systems have distance limitations. If you rely on copper to send signals across distances longer than 100 m, then speeds will drop, network signals will degrade and connection issues will increase.


As more enterprise and data center applications call for data transmission requirements across longer distances, fiber cables step in to save the day. They can support data transmission across much longer distances while maintaining excellent signal integrity.


Knowing how far you want signals to travel is an important consideration when determining which optical fiber cable design to choose: singlemode or multimode fiber. The differences between the two come down to light propagation (how light moves from one point to another). Singlemode fiber carries only one mode of light at once (called the fundamental mode). Multimode fiber carries multiple modes of light at once.


In this blog, we break down four important considerations when deciding between singlemode or multimode fiber for your next project.


1. How Far Signals Need to Travel


As we mentioned, knowing how far your data signals need to travel will help you choose between singlemode or multimode fiber.


Multimode fiber cable excels across short distances while singlemode fiber is made to perform in long-haul signal transmission environments. Here are a few examples of the differences:


  • If there are lots of connection points within a building, then multimode fiber is the best choice
  • If there are lots of connection points across a small campus, then multimode fiber is the best choice
  • If data is moving from one side of town to the other, then singlemode fiber is the best choice
  • If remote offices spanning different cities need to be connected, then singlemode fiber is the best choice


Unlike multimode, singlemode fiber isn’t as limited by distance due to the lack of modal dispersion. Singlemode cables can be spliced together to carry data across several miles (or more).


2. The Upfront Investment Required


Although many factors play a role in determining the cost of a fiber optic network or project, it’s important to understand material cost differences as you choose between singlemode or multimode fiber.


Historically, singlemode cables have been a cost-effective option—but singlemode electronics (transmitters, receivers, transceivers, etc.) were a different story. As hyperscale data centers like Amazon Web Services, Microsoft and Meta use singlemode electronics, however, they’re helping drive costs of electronics down to make them more affordable. As a result, singlemode systems are being deployed more often in data center environments.


When it comes to multimode, the exact opposite has been true: Multimode cables were considered costly while multimode electronics were more cost effective (especially when utilizing LED technology for light generation).


When choosing between singlemode or multimode fiber, it’s important to consider these costs, but also functionality. Depending on the situation, better performance may be worth a higher cost.


3. Application Bandwidth Demands


How much information needs to be sent (the bandwidth of your application) is another key factor. While multimode fiber can support much higher bandwidth as compared to copper systems, singlemode fiber accommodates the most bandwidth of them all.


Because it doesn’t experience modal dispersion effects, singlemode fiber offers nearly limitless bandwidth potential.


Bandwidth capabilities of multimode are impeded by distortion. As the signaling bandwidth increases, reach distance decreases—and vice versa—due to modal dispersion and is typically shown as a bandwidth-distance product (MHz∙km). When rays of light travel along multiple paths and have multiple path lengths, this creates a discrepancy in travel distance among light rays, which is called modal dispersion.


4. Future Network Upgrades


As you plan your fiber network, don’t forget about what it may need to support in the future. Will there be an eventual expansion to more locations? Will bandwidth needs increase as you roll out speed-intensive applications that aren’t in use today?


Because they vary in terms of core size, light source, signal and laser wavelength, singlemode and multimode fiber can’t be interchanged or spliced together. Doing so can result in enough data loss to prevent your network from working properly.


For this reason, it’s important to keep future needs in mind. They can help you determine whether singlemode or multimode fiber is the best choice for today—and tomorrow.


For example, if virtual reality, artificial intelligence, machine learning, big data or medical imaging are on the horizon, then singlemode fiber may be the most appropriate choice to accommodate these technologies down the road.


Learn More Fiber Basics


If you’re ready to learn more basics about fiber optic cabling systems, then our Demystifying Fiber Cabling Systems webinar is a great place to start.


Belden’s fiber experts offer an introduction to fiber cabling systems in under an hour, breaking down and clarifying the basics so you can be confident about upcoming projects involving fiber optic cable.


As the use of fiber continues to rise to support new connectivity demands and bandwidth-intensive technologies, this is information you’ll want to know. Watch it on demand.


Related Posts:

A Space-Saving Way to Manage Lots of Fiber

5 Unique Benefits of Fiber Optic Cable

Fiber or Copper: When to Choose Which Cable