Brownfield fiber roll-out: the alternatives to trenching

There are many ways to clamp down on costs when deploying a brownfield FTTH or FTTP network. Before you create a network design, plan ahead and gather info on what can be reused. What is available underground? What is available above ground? How do different assets and techniques compare in cost and deployment time? In this first of two blogs, we offer some tips & tricks on how to avoid trenching in an underground roll out.

In most cases, going underground is less cost-effective compared to aerial deployment, as you will likely have to dig. However, underground deployment might be the most sustainable solution in the long term as cables are more protected from aggressive weather, birds, temperature variation and other external factors.

In any case, we want to avoid trenching at all costs, because:

  • this happens in the public domain, which means administrative and other hassles
  • civil works are disruptive to the community
  • labor costs make it extremely expensive

Micro trenching or slot cutting is more cost-effective. This is when you put a 0.75 to 1.5 wide by 4 inch deep slot in the ground and within stack microducts, one on top of the other. Though since cables are located close to the street surface, they are prone to damage.

So why not explore some alternatives?

The alternatives to trenching

The presence of other utilities can provide a good alternative to trenching, as their routes and hardware can – partially – be reused. There are plenty of options, but their usability depends on variables such as local conditions and legislation, the state of the infrastructure and its location, and of course cost. 

Infrastructure can be gas pipes, water pipes and sewage – which are usually located deeper underground, phone and electrical cables. And copper, coax or even already placed fiber cables.

Indeed, there might already be some buried fiber in place for other purposes, such as a fiber to the business or antenna network. Investigate these resources for their viability to reuse. The same goes for existing pipe systems. Ideally they have some extra capacity you can tap in to. A conventional pipe consists of a series of (micro)ducts, where fiber can be blown through. If a larger pipe is available, you will likely need to place a new duct or microductbundle before installing the cable.

Textile sub-ducts only take up the space of the cable, so bigger and/or more cables can be installed

As an extra added value, this existing infrastructure usually goes along with structures such as manholes, handholes or even splice closures for easy access. But be careful, since adapting an existing network might cause damage or outage. Which in turn causes frustration and takes time and money to restore. 

If these assets belong to a third party, consider to acquire or lease them. This might prove more economical than placing your own equipment. Although if they belong to a competitor, this might imply additional complexity and cost.

Try textile sub-ducting

When an existing pipe appears to be full, there is a way to ‘create’ extra space. This technique is called textile sub-ducting. Textile sub-ducts only take up the space of the cable, hence bigger and/or more cables can be installed. This technique is also used when classic micro subducting has failed because of dirt or damage in the pipe. 

Sewage deployment can be 30 to 50 percent cheaper than classic trenching

Don’t be afraid of the water

If there are no existing pipes available, explore deploying fiber in the wastewater system. Special sewage deployment and maintenance techniques are needed as this environment can be quite hostile. But If done correctly, this approach might prove to be 30 to 50 percent cheaper than classic trenching or micro trenching.

You can also explore the potable water network. Although this requires specific skills and knowledge as it is no surprise that these networks have high hygiene standards.

In conclusion, there are many ways to bypass civil works. Try thinking out of the box, it might save a lot of time and money. Of course all alternatives have their upsides and pitfalls. They need specific techniques and you might run into issues which you never encountered before. It all starts with gathering information and building that solid plan

Stay tuned for our blog next month on brownfield aerial deployment.