Single or multi-mode fibre - what questions do you need to ask?

Single or multi-mode fibre - what questions do you need to ask?

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When companies are deploying cabling in new locations, there are many decisions to be taken, but one of the most fundamental will be what type of fibre to use. And a key choice will be whether to opt for single or multi-mode fibre. 

There are a wide range of factors to take into account when making this decision, including where you expect to place the cabling, the distances you need to cover and your plans for future growth and maintenance.

In a recent blog, portfolio marketing manager at CommScope Jennifer Duits highlighted several criteria that should be considered when firms are looking to decide between single and multi-mode fibre.

Among the key questions are what your bandwidth requirements will be and if this is likely to increase as a network grows. The environmental factors that will be faced during the deployment should also be taken into consideration, as will the protocol that will be used.

Ms Duits noted the decision between single and multi-mode can be compared to choosing whether to fly or drive for a long distance journey. Each has its pros and cons, with the time and cost only being a part of the equation.

When single-mode fibre will be the best solution

Single-mode fibre can be seen as the equivalent of flying, Ms Duits explained. It's great for long distances and is usually the fastest way to transfer data. Because it only uses a small core with a single light mode, it can reach as much as 10km for certain Ethernet protocols, whereas with multi-mode, modal dispersion acts as a barrier to longer distances.

Single-mode also offers greater flexibility that will be useful if a firm's needs change in the coming years. Ms Duits said: "Single-mode fibre can be used in Passive Optical Networks (PON) where multimode fibre cannot. It is an easy way to increase your bandwidth while lowering future deployment costs."

However, single-mode fibre will typically cost more than a multi-mode alternative to install, so they may be a limiting factor for some businesses where budgets are limited.

The benefits of multi-mode 

On the other hand, if distance is less of a factor for a deployment, multi-mode fibre has its own set of advantages. This solution is ideal for use on campuses where deployers only need to run cabling between nearby buildings, with this being a great, lower-cost option for distances of between 300 and 400 metres. It can be thought of like driving - it may be slower, but it's likely to be cheaper and more convenient if you aren't going far.

Because it offers a larger core size than single-mode fibre, multi-mode is less susceptible to problems created by dirt or other environmental factors, which may make it the better option for areas that are more prone to damage. This also makes it easier to maintain.

"Multi-mode may not be compatible with PON components, but it is preferred when you have an Ethernet protocol," Ms Duits continued, noting that with bandwidth that is able to support the need of 100G and beyond, multi-mode is ideal when the network is needed for Ethernet.

However, one drawback of this solution is that, once it is installed, you cannot easily increase the amount of bandwidth, so you may face a choice in the future between either being stuck with potentially inadequate solutions or expensive recabling projects.

Ms Duits noted that in many campus environments, a mix of single and multi-mode fibre will be needed to deal with differing considerations throughout the environment. She added: "The typical rule of thumb is use multi-mode fibre when you can and single-mode fibre when you must." 

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