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Difference between single mode and multimode fibre

Fiber Optical Cable with Plug Single Mode

Every day, new technologies emerge, and to accompany that we see greater bandwidth usage and network requirements.

Here at OSA we understand that both businesses and consumers demand faster network speed and reliable connectivity. Part of the solution is utilising fibre optic cables in order to meet the needs of advanced technology.

As businesses look to solve these issues, they need to make important decisions about their network infrastructure and that includes whether to use single mode or multimode fibre.

Even though their names would suggest one has higher performance than the other… that’s not actually the case.

They each have their own advantages and are suitable for different applications. So, in order to make the best selection, it’s critical you understand the difference between single mode and multimode fibre. Here we look at these differences so you can support your business’s productivity and make the right cable choice.

Connection with the optical fiber

Difference in construction

Single mode fibre has a small glass core that carries a single mode of light directly through the fibre. Due to this compact structure, light reflection that is created during the transmission is lower and there is less attenuation. This allows the signal to be successfully transmitted over long distances and supports high bandwidth levels.

In comparison, multimode fibre has a glass core up to six times larger in diameter and enables much greater capacity.

More light modes carrying data can pass through a multimode fibre core at any one time… but with more light comes more reflection. This means there is higher dispersion and greater attenuation rates. In multimode fibre, signal quality decreases over distance. Usually, multimode fibres are employed for shorter distances and for data, audio and video applications in LANs.

Shot of Corridor in Working Data Center

Difference in application

While multimode fibre has greater light gathering capacity, it can only provide high bandwidth over a relatively short distance. If you try to utilise multimode cable in long distance applications, it’s likely that you will experience modal dispersion or distortion. This is known as the effective modal bandwidth and is a characteristic determined by the fibre’s bandwidth capability in relation to the reach distance. Increased signal bandwidth will have a decreased reach distance, due to the likelihood of higher distortion.

Single mode fibre does not have the same susceptibility to distortion. All the light passing through the small core travels at a similar speed and arrives at around the same time, greatly reducing the potential for modal dispersion.

This distinct attribute means single mode supports higher bandwidth with less signal loss over further distances when compared to multimode. It is ideal for use in long distance signal transmission applications. We commonly see it used in networks between multiple buildings or campuses, or in remote offices. With single mode fibre there’s really no distance limit.

Fibre optics fibre ends cables

Difference in light propagation

Light propagation is another element where we see a significant difference between single mode and multimode fibre. Single mode has only one type of light propagation, which is step index, whereas multimode has both step index and graded index. Typically, there is less reduction in light propagation in single mode fibre transmissions.

Calibrating single mode fibre requires laser diode based transmission equipment that injects light into the fibre optic cable. For multimode fibre you can use LED-based equipment as it is short distance transmission.

This also equates to differences in the connectors you can use. Single mode connectors have stringent alignment requirements, whereas there is more flexibility in multimode connectors.

This distinct attribute means single mode supports higher bandwidth with less signal loss over further distances when compared to multimode. It is ideal for use in long distance signal transmission applications. We commonly see it used in networks between multiple buildings or campuses, or in remote offices. With single mode fibre there’s really no distance limit.

Servers and hardwares in an internet data center

How to choose between single mode and multimode

The most critical factor when choosing single mode or multimode fibre is the distance you need to cover. Generally, a data centre or localised network will employ multimode fibre, as you can achieve excellent results over 300 to 400 metres.

However, if your networking project needs more than 400 metres of cable, then it is best to select single mode. It can service hundreds of kilometres… if not more, with high bandwidth capacity.

It is essential that you choose the right fibre optic cable to support the technological advancements of your business. We understand that performance and integrity are critical factors in the successful deployment of your network systems.

Here at OSA, we can help determine exactly what your project requires and can support you through the implementation process. If you’d like to speak to one of our fibre optic experts, please contact us today.

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