SubOptic 2025 Presentations: Wet Plant Design - Part 1

Author: Dmitry Kovsh. Subcom employee.
Presentation Available Upon Request.

In his presentation Dmitry focused on designing wet plant for open cable systems. Wet plant is everything in the water up to the beach manhole. The main components are the fibre optic cable and optical amplifiers. I define an open cable system as one where capacity owners manage individually their capacity. This business model involves capacity allocation by fibre pair or a percentage of a fibre pair's spectrum. Big capacity owners own one or more fibre pairs. Smaller players own spectrum called either a quarter fibre pair or half fibre pair. As the name suggests, a quarter fibre pair means the owner has exclusive right to use 25% of the fibre pair's usable spectrum. Similarly for a half fibre pair. Spectrum ownership means the cable delivers usable spectrum on a fibre pair defined by upper and lower frequency limits. The spectrum lying in the frequency range belongs to the owner for the term of the contract. Optical spectrum is measured in gigahertz.

The open cable system minimizes the common management of the fibre optic network. It has been reduced to the wet segment, the front haul fibre from the beach manhole to the cable landing landing station, and the back haul fibre from the CLS to carrier neutral data centres or telecom hotels. Even the back haul fibre is not always a collective decision. In the case of 2Africa one consortium member's main Ghana POP is PAIX. This is where their SLTE (submarine line termination equipment) is kept. Other consortium members keep their SLTEs at the Accra Digital Realty sites. So fibre pair owners under the open cable model can buy or build their own back haul routes and hence select which data centers will house the transponders, DWDM, and add-drop gear.

The open cable maximizes individual owner control and choice. Each owner selects its POPs and all the active optical equipment with the exception of the subsea and optical amplifiers. For example, one 2Africa consortium member could use Ciena gear while another uses SmartOptics or Nokia. This maximum freedom approach speeds network design and deployment. In a large consortium where all network elements are owned collectively, every technology decision requires unanimity or a qualified majority. It takes a lot of time to reach consensus. Nor is it necessarily the case that the best technology fit is the same for every owner or consortium member. If a member is a wholesale carrier, it competes in a very competitive market where services are standardized and consequently price pressure is great. It is more likely to go with a cheaper Nokia or SmartOptics products as opposed to a more expensive system with greater recurring costs (port activation fees) like Ciena. On the other hand, a Tech Giant might go with Ciena because the former enjoys so much bargaining power that it can beat the crap out of the Ciena rep. 😀




Open Cable Concept Advantages Diagram

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