ISPs are Starting to Distribute Gigabit Fiber Internet Over Phone Lines in Some Seattle Areas
ISPs are rolling out Gigabit fiber internet in many metropolitan areas. One of the challenges they face, especially in older multi-dwelling buildings, is network distribution once fiber is in the area and pulled into a building. We are starting to see large ISPs like Century Link address this challenge with an interesting solution that runs over legacy copper phones lines.
Older buildings are often wired up with traditional phone lines – single unshielded twisted pair copper or Cat3 cabling. By utilizing this existing infrastructure, the ISP can bring fiber internet into a building, convert it to Cat3 for distribution, and then convert it to Ethernet with Gigabit internet in a unit. This can be utilized in challenging Fiber to the Home (FTTH) and Multi-Dwelling Unit (MDU) deployments. The technology relies on the G.Fast networking standard and achieves full Gigabit wired network speeds. A typical deployment would like something like the following diagram.
Diagram Showing Fiber to Cat3 Distribution
CASA Systems
Century Link looks to be utilizing CASA Systems to handle the media conversion. Once fiber is brought into the building, it terminates to a Distribution Point Unit (DPU) which is in turn powered by a Network Termination Device (NTD). The DPU converts the fiber line to Ethernet which is punched down into a 66 or 110 phone line block. This is then connected to the existing phone line infrastructure.
Image Showing the DPU Side of a Century Link Gigabit Internet of Phone Lines G.Fast Deployment. This Photo was taken in and Older MDU Building.
At the user end point, conversion back to Ethernet is handled by a Fiber to the Distribution Point or FTTdp Network Termination Device. The FTTdp NTD we see being used is the NDD-0305-01, which essentially acts as a layer 2 bridge modem. The Ethernet port of the FTTdp NTD would be connected downstream to the WAN port of the end user’s router. The router or firewall would be configured normally.
The CASA FTTdp, Image from casa-systems.com
CASA FTTdp Diagram, Image from casa-systems.com
It’s interesting to see this creative solution to delivering high speed internet access in challenging legacy environments.
You can find more information about CASA systems NTD at their website.