To provide ultra-broadband connections to their subscribers, service providers are using the existing copper wire infrastructure. Thanks to new Digital Subscriber Line (xDSL) technologies like VDSL2 vectoring and G.fast, the all-important range from 100 Mb/s up to 1 Gb/s is now within reach. However, such extreme speeds require short copper line, practically up to250 m (0.15 miles).

As service providers move the fibre closer to customer premises, the traditional Digital Subscriber Line Access Multiplexers (DSLAM) that were designed to handle many end users and act as bridge between the fibre network and the last copper drop are no longer practical. Instead, the industry is adopting Distribution Point Units (DPUs), which are much smaller, consume much less power, and are easily deployed in greater numbers close to subscribers. This model is generally referred to as Fibre To The distribution point (FTTdp) or Fibre To The Building (FTTB).

This closer to the customer deployment arise the problem how to power feed the distribution point unit (DPU). And it results that the preferred by service providers method is the Reverse Power Feed (RPF), what means power feed will come from the customer premises over the same copper pair used for data service. This concept looks quite simple and straightforward, but making it work requires careful definition. [1]

Taking into account this new concept the ETSI Technical Committee on Access, Terminals, Transmission and Multiplexing (ATTM) has started the development of ETSI TS 101 548: European Requirements for Reverse Powering of Remote Access Equipment.

The document defines architectures for reverse powering of remote network nodes from multiple customer premises equipment. The architectures describe how to combine reverse power feed with Plain Old Telephony Service (POTS) and data transmission. Options for combining reverse powering with battery backup are also described. The document identifies requirements for ordinary telephone signalling translation when operated over reverse power feed. Start-up protocols are defined that will ensure safe connection of reverse powered systems. Management requirements for reverse power feed and power combining within the remote network node are also specified. [2]

The document shall specify further requirements for:

• End-user self-installation and activation;
• Safety of the customer, as voltage from the Reverse Power Supply Equipment will be present at the copper pair in the customer premises;
• Error-free data transmission in presence of Reverse Power Supply Equipment and its generic noise generation;
• Fair distribution of power supply costs over the active users, even in case of loop length differences;
• Interoperability with other types of power feeding of the distribution point unit.

References:

[1]            François Fredricx, Paul Spruyt, ‘Power from the people: Reverse power feeding’. (https://techzine.alcatel-lucent.com/power-people-reverse-power-feeding)

[2]            ETSI TS 101 548 V1.2.1 (2015-09): European Requirements for Reverse Powering of Remote Access Equipment.