Overview

A mobile network does not need much fibre reaching a cell site. It needs a little fibre reaching a very large number of them — and it needs it at times decided by other people: when a mast goes up, when a wayleave is agreed, when a site is due for upgrade.

That is what makes backhaul a different problem from a backbone route. A backbone duct is sized by capacity. A backhaul duct is sized by how many separate small installations it has to survive. The two look similar on a map and behave completely differently in the ground.

 

What this environment imposes

• Very many sites, very few fibres each. A cell site usually needs a handful of fibres; a backbone route needs hundreds. The fibre count is not what makes the route expensive.

• Sites arrive on someone else’s schedule. A site is connected when the mast is built and access is agreed, not when it is convenient for the duct.

• Densification moves the goalposts. Small cells put more connection points closer together, so the number of separate fibre routes grows faster than the total fibre count.

• Every site is a small job with a full cost. Mobilisation, permits and traffic management are much the same whether two fibres are pulled or two hundred.

• The route stays in service while it is added to. Sites are connected one at a time along a duct that is already carrying traffic.

 

The route, stage by stage

The sequence is the same as any duct route. What changes is the sizing: each stage is chosen for many small additions rather than a few large ones.

Stage	Products	Product pages
1. Pathway subdivision	Fabric Innerduct	/fabric-innerduct/
2. Cable installation	Cable Pulling Tape	/cable-pulling/
3. Entry sealing	Duct Sealing	/inflatable-duct-sealing-system/

 

1. Pathway subdivision — independence, not capacity

A backhaul duct is divided for a different reason than a backbone duct. The purpose is not to fit more fibre into the same bore; it is to make each new site reachable without disturbing the sites already connected.

• Cell count — one or two cells per section is often enough. The point is independence rather than capacity, so where a route has to accept many separate additions, the number of independent cells usually matters more than the total capacity.

• Conduit size — matched to the existing duct, from 1.25″ up to 4″. The fitting matters more than the size, because a route built for repeated access will be worked on many times.

• Custom builds — cell count, dimensions, metre marking and packaging to order, which matters where the same configuration is repeated across many sites.

 

2. Cable installation — a short pull, repeated many times

On a backhaul route the pull is short and repeated. The material that makes the repetition cheap is the one installed with the duct, not the one used on the day.

• Cable Pulling Tape — installed with the innerduct along the whole route, so connecting a new site later is a pull between two chambers rather than a construction job. Selected on width and breaking strength, and available with a detectable trace wire where the route may later need to be located from the surface.

• Cable Pulling Grips and Swivels — used where a heavier feeder cable runs on the same route, selected on cable outside diameter and rated pulling load.

 

3. Entry sealing — a route that is opened often

Every chamber on the route is an opening, as it is on any duct route. The difference here is frequency: a backhaul route is opened far more often than a backbone route, and the seal has to accept a small cable while still closing the duct around it.

• Inflatable duct sealing system — seals the duct around the cable where it enters a chamber.

• Reusable / self-inflating sealing bag — a removable seal, which on this application is the normal choice rather than the exception, because the route will be re-entered.

• Duct plugs — selected on duct inner diameter and type: blank, single-cable, multi-hole or split.

 

Choosing the innerduct for a backhaul route

If you are choosing…	Start with	Because
By access — how many separate additions the route has to survive	By Cell Configuration	The cell count sets how many additions can be made independently; 1, 2, 3 and 4 cell versions are each a distinct product
By fit — what duct it has to go into	By Conduit Size	Conduit size sets physical compatibility with the existing bore, from 1.25″ to 4″
By project — the same configuration repeated across many sites	Custom OEM	Cell count, dimensions, metre marking and packaging made to order

 

What goes wrong on a backhaul route

• Designing for capacity instead of for access. A duct that is generously sized but not divided still has to be opened for every new site.

• No tape in the first installation. On a route that is added to site by site, the tape is the mechanism, not an accessory.

• One cell for everything. Once two services or two operators share a cell, neither can be worked on alone.

• Seals that cannot be re-opened. A route that is opened repeatedly should be sealed with something that can be re-entered.

• Treating a backhaul duct like a backbone duct. The two are sized by different things — one by capacity, the other by the number of separate additions.

• Ignoring the bend at the chamber. Many small pulls at the same chamber means the corner is worked repeatedly, and that is where cable is damaged.

 

Where this fits in the route

This is the access side of the outside plant route: the same sequence — subdivide, pull, seal — sized for many small additions rather than a few large ones.

Related applications: Outside Plant (OSP) — Duct & Pathway Systems, where the route is built for capacity; FTTH and Access Networks, where the final leg reaches the subscriber; and Data Centres and In-Building Pathways, where the same subdivision logic is applied inside a building.

Related product ranges: Fabric Innerduct, Duct Installation Systems.

 

Datasheet and ordering

Duct and pathway materials are ordered against the route they have to fit, so the data sheet is issued against your specification rather than published as a fixed table. Tell us the following and we will confirm the materials, the datasheet, a sample and the price together.

• The duct: internal diameter, length between chambers, and whether it is new or already in service.

• What is already in it, if anything.

• How many sites the route has to reach now, and how many later.

• The cable being installed: type and outside diameter.

• Whether the route will be added to while it is carrying traffic.

 

FAQ

Why is backhaul different from a backbone route?

They are sized by different things. A backbone duct is sized by the capacity it has to carry; a backhaul duct is sized by the number of separate small installations it has to survive. The fibre count is low; the number of separate jobs is high.

How many cells does a backhaul duct need?

Enough to keep each addition independent. One or two cells per section is often sufficient, because the requirement is access rather than capacity.

Does a cell site need many fibres?

Usually only a handful. That is why the cost of a backhaul route sits in the number of separate installations rather than in the fibre count.

How does 5G change the requirement?

Densification puts more connection points closer together, so the number of separate fibre routes grows faster than the total fibre count. A duct that is easy to add to becomes more valuable, not less, as the network densifies.

Can a new site be connected without re-opening the route?

That is what pre-installed pulling tape is for. Where tape was installed with the innerduct, connecting a new site is a pull between two chambers rather than a construction job.

How do we get a datasheet?

The data sheet is issued against your route. Send the duct size, what is already in it, the number of sites and the cable, and we will confirm the materials and the data.