What is Blown Fibre?

09 August 2019

I’ve covered in past blog posts what fibre optic cables are capable of, if you’ve yet to read, I’d recommend reading one of our recent posts, what are the benefits of fibre optic cabling.

In the previous posts, I’ve discussed some of the benefits that fibre optic cabling provides, and we’ve discussed the difference in Singlemode and Multimode cabling, and even the difference between fibre optic cable constructions.

However, there are many ways to install a fibre optic link.

While conventional fibre optic cables, such as tight-buffered and loose tube provide a quick means to install a single cable; they don’t offer the same flexibility as blown fibre…

What is Blown Fibre?

Blown Fibre takes the elements that make up a conventional fibre optic cable and separates them.

When you break down a fibre optic cable, you have the sheathing and the fibre cores.

In a blown fibre optic installation, these elements are installed separately.

Initially, a “Microduct Bundle” or “Tube Bundle” is installed, this provides many internal microducts.

Tube Bundle

This is the external barrier; in a conventional cable, this would be the outer sheathing.

Despite this being blown fibre, the usual suspects are found with tube bundles capable of being directly buried, rodent-proof (CST), low smoke zero halogen and even low fire hazard systems.

Alongside providing the external sheathing, this tube contains a bundle of microducts.


Microducts are contained within a tube bundle.

In a usual tube bundle, anywhere from 1 micro duct, all the way to 24 micro ducts can be contained.

Each duct can subsequently house up-to a 12 bundle of fibre, also known as a 12 core fibre.

Pretty smart, right?

How are blown fibre cables installed?

An average blown fibre installation is carried out in two phases.

Initially, the tube needs to be installed. A backbone tube will be installed to provide a fibre optic ‘motorway/highway’, then from this, your A Roads will be installed, these are usually smaller capacity tubes which will then either be installed to tenant units, communication rooms/cabinets or even office spaces.

Once the tubing has been installed, the selection of fibre optic cable will be blown through the micro duct, whether this be a multimode or single mode fibre, 4 Core or 12 Core and beyond.

A special tool, known as a blowing head, is then used. This enables for an air-tight seal to be made around the microduct, where compressed air is forced into the microduct, creating a viscous drag for the fibre bundle to be drawn through.

The blowing of the fibre optic bundle is a relatively quick and efficient process, there is no longer a requirement for ceilings or floors to be exposed, furthermore, access should only be required at the termination points.

Once the fibre optic bundle is installed end to end, the fibre optic cable can then be fusion spliced just like any other fibre, and as an end-user, there would be no operational or identifiable difference.

What are the benefits of blown fibre?

So although we have to install the elements separately, this opens a whole new world of possibilities.

When installing the blown fibre tube bundle, it is common to over-install, so whilst current requirements only dictate 1x 12 Core OM4 Fibre, later down the line, you may need another, or new hardware dictates OS2 instead of OM4?

The beauty of blown fibre is that you have another micro duct sat vacant.

At this point, you can blow a new fibre down a vacant micro duct without having to disrupt either your current fibre connection, or even lift a ceiling tile/floor tile. Once the tube bundle is installed, it’s there for the future.

Once the tube has been installed, there is no longer any requirement to lift ceiling or floor tiles or create disruption throughout the installation areas. This means installations can be carried out, and nobody would even know.

If you want to discuss whether blown fibre could provide benefits to your organisation, do not hesitate to reach out to our team on 01604 422722.