From 560 Mbps to over 400 Tbps — South Africa’s Internet revolution – MyBroadband

The cable infrastructure enabling South Africa’s access to the Internet has drastically improved over the past 25 years, employing new means of multiplexing and increasing capacity from 560 Mbps to over 400 Tbps.

As online applications started consuming more bandwidth, with the advent of media-rich websites, social media, YouTube, and Netflix, user demand for data naturally increased.

Thanks to this increase in demand, the technology to transmit data around the world is constantly improving.

For instance, the most recent breakthrough in fibre transmission speed was achieved by researchers at the Aston University Institute of Technology and Engineering, who managed to achieve transfer speeds of 301 Tbps over a single wavelength.

This was done using existing fibre optic cables and transferring the data via the E-band and S-bands — which are not used in commercial wires. The total data transferred is the equivalent of transferring 1,800 4K movies over the Internet in one second.

As mentioned, this was achieved by transmitting data through a single wavelength. However, fibre strands use multiple wavelengths when transferring data.

The wavelength refers to the spectrum of light used to transmit data, most commonly 850 nanometers (nm), 1,300 nm, and 1,550 nm.

For visible light, which is in the 400–700 nm range, the wavelength determines the colour of the light.

The wavelength affects the attenuation of light transmitted through a medium caused by scattering and absorption.

Scattering refers to light bouncing off molecules and atoms in the glass, and light absorption occurs in specific wavelengths caused by water vapour in the glass.

Multiple carrier signals can be transmitted over a single optical strand by using different wavelengths through wavelength-division multiplexing (WDM).

Multiplexing refers to the packaging of all the wavelengths into one signal.

WDM also allows for bidirectional communications over the same strand of fibre, which acts as an alternative to a fibre pair where one strand receives and the other transmits a signal.

One of the original submarine fibre cables to connect South Africa to the rest of the world, the South Atlantic 3 (SAT-3), has four fibre pairs and uses WDM technology and Erbium-doped optical fibre amplifiers.

Optical amplifiers can amplify optical signals without first converting them into electrical signals.

In a doped optical amplifier, the optical signal and pump laser are multiplexed into a fibre strand doped with ions that stimulate the photons. Erbium ions are used in the SAT-3 amplifiers.

When the South Atlantic 3 (SAT-3) submarine cable landed in South Africa in 2001, the only other cable connecting the country to the rest of the world was the SAT-2 cable, which had a capacity of 565 Mbps.

SAT-3’s design capacity when first installed was 120 Gbps. Today, the SAT-3 cable has a design capacity of 340Gbps.

The next cable installed was the privately owned Seacom cable in 2009, which also employs Erbium-doped optical fibre amplifiers and over 150 repeaters along the entire cable system.

Repeaters, which are placed tens of kilometres apart along the cable, increase the range of an optical signal.

Seacom’s initial capacity was 1.5 Tbps and has been upgraded several times over the years. In 2020, its design capacity was boosted to 3.2 Tbps. Today, the cable has a capacity of 12 Tbps.

The Eastern African Submarine System (EASSy) cable was the next to land in South Africa in July 2010, initially using a configuration of two fibre pairs and 68 wavelengths per pair, using 10 Gbps per wavelength technology.

Its initial design capacity was 680 Gbps, which was upgraded to 4.72 Tbps the following year using Alcatel Submarine Network’s (ASN) 40 Gbps wavelength technology.

In 2014, ASN’s 100 Gbps technology was used to upgrade EASSy to 10 Tbps.

EASSy’s latest upgrade employs Ciena’s GeoMesh Extreme technology, giving the system a total capacity of 36 Tbps and the South African section a 10 Tbps capacity.

The West African Cable System landed in South Africa in 2012 with a design capacity of 5.12 Tbps, an increase from the planned 3.84 Tbps.

The cable employed four fibre pairs, 128 wavelengths per pair, and 10 Gbps per wavelength technology.

In December 2015, Huawei Marine upgraded the cable, increasing its design capacity to 14.5 Tbps using 100 Gbps per wavelength technology.

The cable underwent another upgrade in 2019 to support 32 wavelengths at 100 Gbps each.

The following year, the Melting Pot Indianoceanic Submarine System (METISS) cable landed in South Africa with a design capacity of 24 Tbps.

In July of the following year, another cable, the Africa Coast to Europe (ACE), landed in South Africa with a design capacity of 20 Tbps using 40 Gbps WDM technology.

The initial design capacity was 5.12 Tbps. However, this was upgraded when the final stretch of the cable landed in South Africa.

Google’s Equaino cable, which arrived in South Africa in August 2022, introduced new fibre technology. It employs 12 fibre pairs of 12 Tbps each and uses spatial multiplexing.

Unlike WDM, which is used in single-core fibres, spatial multiplexing uses multi-core fibres to offer multiple spatial channels within a single fibre.

Two years later, the first section of Facebook-backed 2Africa cable went live, offering a capacity of up to 180 Tbps. The cable uses 16 fibre pairs and will be the first cable connected to Africa to use wavelength-selective switching (WSS).

WSS allows communications networks to switch signals between optical fibres on a per-wavelength basis.

The table below summarises the key submarine fibre cables that have provided connectivity to South Africa since 1993, and how their capacities have changed over the years.