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Programmable computing platforms guarantee performance in FTTH networks

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Europe has adopted fibre to the home as the technology for last-mile data connections, ultimately replacing copper-based technologies for business and home connectivity. There are many technical reasons behind the move, and high-speed programmable computing platforms are helping to make this technology a reality.

By Paolo Novellini, Principal Engineer, Adaptive and Embedded Computing Group, AMD

Of the many solutions available for last-mile connectivity, none offers the same advantages as FTTH. More importantly, FTTH is an inherently reliable technology. It relies on passive optical networks (PONs) rather than active devices that are prone to failures and power outages.

Wired solutions such as ADSL are also passive, but too slow to deliver the required performance. In contrast, fibre itself is not subject to any speed limits and the electronics can be upgraded over time to keep up with technological improvements. In a PON network, the electronics are only located at the head office and the user's home (modem) - not in street cabins. In addition, FTTH technology offers an ideal complement to the rapidly growing 5G applications. Fibre optics is the only solution that can cope with the bandwidth and latency requirements of IoT.

There are also environmental benefits, as theCO2 output of a passive network is significantly lower than that of an active network.

Despite these advantages, Europe has been slow to move away from copper connections. One reason is the cost of retrofitting the infrastructure, with the capital investment falling on operators, who have little incentive to upgrade their network with copper cables. In the absence of alternatives, operators see no economic benefit in upgrading their network. However, there has already been considerable progress in the adoption of FTTH technology.

The Nordic countries are at the forefront of this process because they were not tied to traditional copper networks. Spain and Portugal are leading fibre adoption, while the situation is stagnant where there is a strong presence of incumbents. For example, Italy and Germany are lagging behind in fibre adoption.

A single operator: a winning business model
Prior to 2015, FTTH adoption was hampered by the cost of deploying passive networks. In addition, investors were constrained by implementation uncertainties: in particular regarding the scale of investment and the uncertainty of returns.

The solution came via regulators and policy makers in the form of a wholesale-only business model, where public and private investors can invest in new companies that own the passive network and sell services exclusively to operators at a regulated price. The Nordic countries were the first cases where local authorities invested in their own network. Stokab was a pioneer in Sweden and was followed by the network operator in Italy (Open Fiber), along with Onivia in Spain, Siro in Ireland and CityFibre in the UK.

This new model limited to wholesale distribution represents a significant step forward in last-mile transmission, as it introduces competition in an area where the historical model has dominated for several decades.

Technology overview: evolution of standards in FTTH technology
Passive optical networks are based on a point-to-multipoint structure. In the direction of the user, the Optical Line Termination (OLT) continuously transmits the same data to all Optical Network Units (ONU). Each ONU is only able to decrypt its own part of the data. In the direction of the exchanges, each ONU is assigned a time interval during which it can transmit data to the OLT. Only one ONU can be active at any given time.

Figure 1: Chronological evolution of PON technologies and related line speeds

OLT terminations at headquarters dynamically orchestrate the time intervals for UN units and these do not have to be balanced against contractual conditions. Market adoption, which includes development and installation time, occurs about five years later (Figure 1). The line speed to exchanges and users depends on the generation of PON networks in use (Figure 2) and the evolution of FTTH protocols is linked to the availability of faster electronic components.

Figure 2: General architecture of a PON network with details of the transmission to the exchanges.

Installed fibre cables are a resource that should last for several decades, so they do not change from one generation to the next. However, ONUs can be optionally upgraded when the operator upgrades an OLT termination. This allows operators to upgrade their installed network over time without any problems by monitoring the needs of their customers.

Future developments will focus on increasing bandwidth (user and central side) and reducing atmospheric emissions per route. Passive infrastructures are significantly better than active copper infrastructures, simply because they do not consume energy. It is likely that the HS-PON standard will follow 25GS-PON very closely. The market will decide the eventual success of the 25GS-PON technology.

European Commission framework for the "Digital Decade" 2030
The EU's objectives for the adoption of FTTH technology are set out in the 'Digital Decade' plan, which has the ambitious goal of providing Gigabit-class connectivity to all households by 2030. Alongside this objective, the phasing out of copper connections is a progressive goal, in view of the emission-neutral advantage of using a passive network.

The disconnection of copper networks is also part of the Green Deal (2050), which operates on two levels: subsidising the installation of fibre in areas where the investment would be profitable; and regulating the business model in wholesale distribution only. The Digital Infrastructure project alone has the ambitious goal of providing 100% fibre coverage to households by 2030.

In addition to fibre connectivity, the 'Digital Decade' project sets out clear and ambitious plans for a range of technologies such as:

  • digital transformation of the public sector and private enterprises.
  • digital identity.
  • quantum computing.
  • rebalancing of silicon production.
  • national secure cloud.

Fibre to the Home" (FTTH) is the enabling technology behind all these plans, and the development of optical line termination devices is a critical element. The Versal Adaptive Computing Acceleration Platform (ACAP), with its support for burst synchronisation, is the ideal platform for OLT terminations.

 

Figure 3: The Versal Adaptive Computing Acceleration Platform (ACAP), a fully software-programmable heterogeneous computing platform that delivers significant performance improvements


Versal ACAP: the ideal platform for OLT terminations in FTTH technology

Versal is a programmable platform based on TSMC's 7nm technology, with transceivers capable of operating natively up to 112G. All transceivers (up to 140 in a single package) are individually programmable and can support the speeds required by an HSPON network in a multi-port OLT termination. It is also compatible with previous generations with lower transmission rates to OLT terminals.

The platform is equally suitable for more common network applications such as Ethernet, including MAC and FEC subsystems, which are fully supported for connectivity to other devices or optical connectors. Its programmable logic unit can be used to implement any specific functionality that can differentiate products.

A particular advantage of Versal transceivers is the ability to measure the latency associated with serial interfaces at runtime. This makes the device extremely attractive for time-critical applications (IEEE1588), not to mention its ability to have every function in a single device, which can be reprogrammed at any time.

Further potential data from "other" sources:

Figure 4: This is the state of play in the European Union in May 2021. Source: IDATE DigiWorld for FTTH Council Europe.

Figure 5: The objectives for the 'Digital Decade'. Source: European Commission

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