Single-Mode Fiber vs. Multi-Mode: Making the Right Choice

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The choice between single-mode or multi-mode fiber deployment can be a critical decision for a data communications network. In this article, we’ll use the metaphor of traveling to a family vacation destination to help explain and simplify what can be complex issues surrounding the single-mode fiber vs. multi-mode decision.

So you want to take the family on their next adventure. What’s your destination, and how will you get from point A to point B?  In line with our travel metaphor, the decision in selecting single-mode or multi-mode fiber optic cable is a similar question regarding whether you fly through the air or travel by ground to get there.

When deciding on whether to fly or use ground transportation, things you would consider include:

  • What is the size of my travel group?
  • Is my group finite, or will we be adding individuals along the way?
  • What is the quickest route to my destination?
  • How expensive is this trip going to be?
  • Can we make this trip with the money we have on hand?
  • What will the traveling environment be like?
  • Will we be traveling in comfort?
  • What is the purpose of our trip?
  • Will we need to bring extra stuff on our trip?

If you can answer all of the above, then you can make an informed decision and continue planning the rest of the trip like lodging and what you will do when you get there.

When deciding between single-mode and multi-mode fiber, similar criteria applies. For example:

  • What is the required bandwidth?
  • Will you need to plan for network growth?
  • How far will your signal need to transmit?
  • What is your budget?
  • What are the environmental factors?
  • How important is routine maintenance to you?
  • What protocol will it be used for (i.e., Ethernet, PON, SONET, etc.)?

Let’s explore how single-mode and multi-mode fiber measure up.

Air travel with single-mode fiber?

When comparing single-mode fiber vs. multi-mode options, single-mode, much like air travel, can get you to your destination much faster. Based on fiber performance calculations, single-mode fiber can be used in distances up to 10 km (6.21 miles) for certain Ethernet protocols. Multimode fiber is limited in its reach. The issue supporting the long-distance transmission of single-mode fiber is the small core of the fiber; it propagates a single mode of light.  With multimode fiber, modal dispersion is one key factor impacting distance limitations.

Single-mode fiber is also like air travel because the planes, or transportation equipment, akin to the electronics with single-mode fiber (high-end lasers), cost more than the equipment to travel by land (LEDs and VCSELs in the case of multi-mode fiber). You pay more for non-stop air travel in the same way you pay more to have one long fiber run.

Single-mode also provides flexibility for future growth or modification. Additionally, single-mode fiber can be used in Passive Optical Networks (PONs) where multimode fiber cannot. It is an efficient way to gain bandwidth while decreasing deployment costs. That way if an unexpected traveler joins the trip, they can be easily accommodated within your trip plan. You won’t have to buy another ticket to have them fly with you.

Land Transport With Multi-Mode Fiber 

For the most part, multi-mode fiber aligns with the decision to travel by land. It’s great for short distances — between 300 and 400 meters (328 and 438 yards) — and is a low total cost alternative to air travel (i.e., single-mode fiber due to the electronics/equipment involved). For short fiber runs, say, between buildings, multi-mode fiber is the right choice.

Importantly, multi-mode fiber is much easier to maintain vs. single-mode fiber. Multi-mode fiber has a larger core size so it’s less sensitive to the environment. A negative to using multi-mode fiber is bandwidth limitations — you may not be able to increase it if you need more in the future. In other words, once you buy your plane ticket, you might be able to move from coach to first class, but you will need to buy another ticket if an unexpected traveler joins your trip at the last minute. 

Application and Cost Considerations

Another key factor in determining single-mode fiber vs. single-mode is the electronics involved. Single-mode requires sophisticated laser technologies to drive the signal which increases the cost of the total solution. Multi-mode systems employ lower-priced light sources (i.e. LEDs and VCSELs) to launch the signal. This makes for a more cost-effective solution.

As you can see, there are good reasons to use both single and multi-mode fiber solutions, depending on your network applications. Whether an application or cost focus, WESCO and CommScope are here to help in your single-mode fiber vs. multi-mode decision.

 

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The opinions expressed in this piece are solely CommScope's. They do not necessarily represent WESCO’s views. 

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