By Jose M. Enriquez
There has been a long-standing debate as to which is better for aerial cable installations: Lashed Cables or All-Dielectric Self Supported Cables (ADSS). While there are advantages to both, depending on your network architecture and requirements, we will focus on the advantages of ADSS cables for Municipal and Electrical Co-Op Networks, and particularly on a new solution to an old problem: how to manage cable drops in FTTH scenarios.
Mark Boxer, technology manager at OFS, presented us with their recently launched, patent-pending, Sherpa Cable Management System. M. Boxer has been working with ADSS cables for decades, he was secretary of the IEEE-1222 Standard Committee (the IEEE Standard for Testing and Performance for ADSS Fiber Optic Cable for Use on Electric Utility Power Lines) as it went from being a draft to being a standard; hence, he is quite familiar with the advantages of ADSS cables when used in proximity to power lines.
ADSS had been historically used in new builds by electrical co-ops and municipalities for multiple reasons: ease of installation, speed of deployment, safety, and overall lower costs
Cost of deployment
For strand and lash, just the make-ready process of the poles could be as costly as the installation of an ADSS cable itself, and that translates into time and money not spent deploying more fiber. Contractors experienced with ADSS installation will often charge less to install an ADSS cable vs a lashed cable, primarily because ADSS is a one-step process.
Relative deployment costs – ADSS vs Lashed
ADSS, as a non-metallic cable, takes away the bonding and grounding requirements, reducing potential safety issues.
The Challenge with ADSS in FTTH Networks
Municipal and Electrical Co-Op Networks typically don’t like to add more metal to their poles; however,“the Achilles’ heel for ADSS cables has been how to manage the drops, and what happens to an ADSS trunk cable when you attach drop cables to it?” said M. Boxer.
What if we could attach drop cables to an ADSS Trunk Cable?
If we could simply attach the drop cables to the trunk cable, some of the benefits would include the following:
- Eliminate the “make-ready” process required for strand and lash
- Maintain an all-dielectric system by eliminating the need for a metallic strand
- Significantly reduce the installation time and cost (ADSS installation is roughly 30% faster than strand and lash)
- ADSS cables require fewer pole attachments (trunk and drop could share the same attachment)
- Can conserve pole space and make it aesthetically clean
- Significantly reduces safety concerns (less risk of electrical shock)
A new solution to an old problem
OFS has come up with a patent-pending dielectric solution for attaching dielectric drop cables to an ADSS trunk cable (or an ADSS cable to a neutral cable). The Sherpa CMS ADSS Cable management system is a dielectric way to attach cables within a span.
The Sherpa CMS attachment is made of Ethylene Propylene Diene Monomer Rubber (EPDM Rubber), a material that has been widely used in the outside plant for years with a wide operating temperature range and with excellent environmental and weather resistance properties.
A new solution to an old problem
There are versions for attaching flat or round drop cables to the ADSS trunk cable, and another version for attaching an ADSS Cable to a Neutral Cable . This last one is particularly useful to reduce the span length, say when crossing a road, rather than having a full span of 400 ft, you can effectively reduce it to 200 ft by installing this attachment in the middle (particularly useful under ice load conditions).
OFS’ stress/strain testing shows that when trunk and drops are mechanically coupled, they share the load. Drops can also increase their range when coupled to the trunk; and, while coupling may slightly reduce the range of the trunk depending on circumstances, when used per recommendations you can expect the usual reliability performance of the fiber optic cables.
The Sherpa Cable Management System offers a solution that can help save time and money when building Municipal and Electrical Co-Op FTTH Networks. Deploying an all-dielectric network also reduces the risks involved and this system helps organize the drop cables, extend their reach, and preserves an aesthetic look for the local communities where they are installed. As always, there is no one solution that is perfect for every network; but this is a solution worth trying if you are just about to build an FTTH network.