According to a report by Capgemini, energy consumption accounts for 20 to 40% of operators’ operational expenditure (OPEX).

It comes as no surprise then, that more than one-third of operators have started implementing net zero policies. Those who successfully increase their energy efficiency will benefit from enviable cost savings, an ESG status and a powerful competitive advantage.

Trends like miniaturisation, smart devices and inventory optimisation are a few solutions telco operators can implement to help them accomplish their sustainability targets.

100G coherent modulation

To keep up with increasing data demand, network operators and data centre owners have migrated to 100G connectivity. The QSFP28 optical module is widely used to intermediate 100G connections, but it also allows users to scale their operations to 200G and even 400G.

Third-generation QSFP28 100G ZR4 modules feature a new internal SOA amplifier, which reduces power consumption by 1 W. These modules allow 100G transmission over dark fibre using LanWDM technology. Saving 1 W per module makes a big difference, resulting in an annual saving of around 18 kWh on just one point-to-point connection.

So far, solutions based on electro-absorption modulated lasers (EML) have been more energy-intensive but have enabled transmission over longer distances (above 10 km) and at higher data speeds compared to directly modulated laser (DML) solutions.

EML lasers are characterised by a much higher extinction coefficient, a 10 to 15% higher optical eye pattern margin factor and less chromatic dispersion. The latest EML laser solutions, used in 100G per 10 km modules, have a power consumption of less than 3.5 W (QSFP28 100G LR4 10km modules). In this case, the power consumption saving is due to the use of a less power-intensive CDR chip. In terms of power consumption, this puts the solution on a par with a DML laser-based module.

400G modules

For the latest 400G modules, the potential for reducing power consumption is even more considerable. The latest developments use Digital Signal Processors (DSP) for direct laser control, making it possible to reduce power consumption by more than 3 W. This will result in power consumption savings of half to several watts per link.

These 400G modules can be installed directly in the equipment, avoiding the need to invest in additional muxponders and transponders and cutting the initial installation price by more than 50%.

IP-over-DWDM solutions

When there is a need to transmit higher rates like 800 Gbit/s using a single fibre pair, this can be realised using dense wavelength division multiplexing (DWDM) technology. However, DWDM requires the use of amplifiers, transponders or muxponders, which generates the need for more energy resources and, of course, additional rack space.

IP-over-DWDM solutions are therefore gaining popularity. This technology works by mounting IP equipment directly on transport optical modules. By omitting muxponders, transponders and grey optics from the structure, operators can achieve significant energy saving. Depending on the network area, it can reach saving levels ranging from 70% at the network edge to 90% at the network backbone.

O-Band – transmission without amplifiers

Operators who need a long-distance transmission of up to 25 km can benefit from O-Band technology. This solution saves almost 900 kWh per year for a single 8×100 Gbit link.

O-Band technology consists of passive multiplexers and optical modules in the form of QSFP28 interfaces. The great advantage of O-Band technology is that it does not require the use of optical amplifiers, as transmission over distances of up to 25 km is achieved through a power budget derived from the optical module itself.

At the same time, O-band is not sensitive to chromatic dispersion, which eliminates the need to use chromatic dispersion compensators, resulting in a signal that is not distorted. By using nCP4 processor technology on Silicon Photonics Tower Semiconductor’s PH18 platform on top of O-band technology, it is possible to reduce power consumption required for the demanding PAM4 modulation.

For telecom operators, energy saving starts at the network level. An optimised network containing smart devices, innovative transmission solutions and less energy-intensive equipment is key to keeping up with data demand in a sustainable way. Innovative strategies such as IP-over-DWDM and O-band transmission or smart technologies like 100G modulation, new EML lasers and the latest 400G modules can be implemented to ensure operators reach their net zero targets, while also saving costs.