What are the Differences between Singlemode and Multimode Fibre?

25 January 2018

Optical fibre has become commonplace in most networks, and this is mainly due to its huge advantages over standard twisted-pair copper cabling.

Optical fibre comes in a variety of different options, for more information see our blog post on the different types of fibre optic cable explained

When considering fibre optic cables, it is essential to consider both multimode and single mode fibre types, they both have their benefits, but what are they?

What are the advantages of singlemode fibre?

Singlemode fibre has a 9-micron diameter core surrounded by a 125-micron cladding.
Because of this small diameter, it only has enough capacity for a singlemode of light to traverse down it. This leads to a low amount of attenuation allowing for the signal to travel further with lower loss.

Singlemode is primarily utilised within long-haul environments, and if your business has a leased fibre line, this is likely what you will have installed.

However, singlemode fibre is becoming increasingly used even in shorter haul installations due to its ability to be more versatile in future applications.

For example, it is already capable of providing up to 100GbE over distances of up to 40km (100GBASE-ER4) using just a single pair of cores; this is something which multimode can only be jealous of! We think this amount of bandwidth should be enough for a while!

Unmistakably, this all has to come at least one disadvantage, cost. While the actual cable is usually cheaper to purchase, due to the long haul nature, instead of LEDs, high-quality lasers are required within the active hardware such as transceivers. This causes them to be more expensive to purchase.

It is also important to remember that, with a small core diameter, it is ever more essential to ensure that the installation is carried out to a high standard too. Due to its small core size, it is hugely important to keep the fibre faces clean at all times; we recommend that best practices when handling the fibre are adhered too.

In summary, we feel that if you are happy paying extra for active hardware to gain a more future proof network and understand the requirements to keep fibre infrastructure operating well, singlemode fibre is a good choice.

Pros:

  • Low loss over large distances allowing for high throughput over distances of up to 40km.
  • Low core count required for high throughput unlike multimode.

Cons:

  • Due to the small core size, needs to be kept clean at all times.
  • Higher cost when purchasing active hardware such as transceivers and media converters.

What are the Advantages of Multimode fibre?

Multimode fibre packs a bigger core size, typically 62.5 or 50 microns, because of this larger core size, there is space for multiple modes of light to traverse its length. Allowing for multimode applications to utilise lower quality and thus lower cost LEDs or lasers within the transceivers.

Because of the higher dispersion within multimode fibres, the signal progressively loses quality the further it travels, causing the bandwidth to distance ratio to be much lower than singlemode making it less suitable for long-haul solutions.

For many organisations, Multimode fibre is go-to when linking cabinets, switches and servers that are short distances apart. Currently, there are four current revisions of multimode fibre that are available to deploy; each an improvement on its predecessor.
As you can see below in the table, newer technologies can even offer 100GbE, however, to do so you will need to use more cores than a singlemode cable.

Because of the lower transceiver costs coupled with the throughput that can support current requirements, we feel it is the best choice when directly linking switches and servers.

Multimode fibre while ideally is fusion spliced to provide a lower loss is easier to terminate than singlemode which can provide savings within the labour.

On-going maintenance when working with a multimode fibre infrastructure is usually lower too, and this is due to the larger core size. Smaller dirt and dust particles will not impact the link quite as much as a singlemode where even the slightest particle can bring the link to a complete halt.

In summary, we feel if you are budget conscious when procuring network hardware such as SFPs and you do not foresee your bandwidth requirements surpassing the above limitations within the lifetime of the fibre, then multimode is a better choice.

Pros:

  • Due to the simple light-emitting technology utilised, there are cost savings to be reaped when purchasing hardware such as transceivers.
  • The larger core size gives you a larger margin of error when handling the components.

Cons:

  • As the technology uses lower grade LEDs or lasers, less data can be carried over the fibre in comparison to singlemode.
  • When deploying high bandwidth links, it is usual to require multiple pairs of cores, quickly utilising a full fibre – planning when installing multimode is required.

Conclusion

In conclusion, there are multiple differences between both singlemode and multimode fibre optic cabling. However, these differences are drastically different.

There is no one-size fits all when specifying fibre optic cabling, therefore if you are uncertain on which to chose for your application, contact us today on 01604 422722 and speak to one of our consultants.