Subsea Cables & Internet Infrastructure

1. The submarine line termination equipment, consisting of active electronics and transponders (lasers and optical receivers), was traditionally kept at the cable landing station. This began changing when carriers wanted to own and manage their own dedicated capacity (fibre pair or spectrum slice). Telekom Malaysia was an early example. It took two fibre pairs on the ASE cable as opposed to a fraction of the consortium lit capacity. Later the hyperscalers crystallized this evolution in the open cable model which limits common ownership to the wet segments. Each owner has either fibre pairs or spectrum and makes its own decisions concerning where to place the SLTEs. Because cable landing stations are not designed as large carrier neutral interconnection points, the SLTEs are almost always housed in a cage at a carrier netural data center. It is this flexibility in choice of location and equipment vendor that makes the open cable model so appealing. It also facilitates hyperscalers build...

Dr Kowalski is a Nokia employee who collaborates with ASN. His presentation on the first day of the conference is a good subsea cable primer.  The transmission equipment is known as the submarine line termination equipment or SLTE. It has three key components. Encoding involves taking the digital input and converting it into a series of laser commands according to the modulation scheme. FEC or forward error correction adds redundant bits called parity bits that help the far end FEC to detect and correct payload mistakes. It is a bit like a router creating the checksum field in the IP packet header. Once quality is control is completed, the laser sends the optical signal. Its ever weakening light travels the fibre until it is passively boosted by erbium doped fibre in the amplifier that has been raised to a high energy level by pump lasers. At the far end of the linear transmission the steps are reversed. The optical receiver takes the light signal and converts it into the appropria...