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Trans-Caspian cable: the terrestrial test starts now

The first fiber across the Caspian is now on the seabed. Its value for Europe and the Balkans will depend on terrestrial diversity, capacity disclosure, and a credible RFS.

Yuliy Nushev6 min read

CEO, Sofia Connect EAD · Honorary Consul of Georgia in Bulgaria

The first fiber-optic cable laid across the Caspian Sea has reached the Kazakhstan coast. The 380-kilometre Trans-Caspian system, connecting Sumgait in Azerbaijan with Aktau in Kazakhstan, has completed its most visible construction milestone and is still targeting full operation by the end of 2026. That matters beyond the two landing points: it adds a new physical layer to the Middle Corridor, but its usefulness to European carriers will be determined less by the headline capacity than by the terrestrial routes, interconnection model and protection regime on either side of the sea.

The offshore campaign moved quickly. The Kazakh Ministry of Artificial Intelligence and Digital Development said the cable vessel departed Baku after the cable had been transported from Kazakhstan, with direct laying expected to take 15–20 days in suitable weather. On 5 August, Qazinform, citing the ministry, reported that the subsea cable had reached Kazakhstan’s shoreline. The offshore phase therefore moved from planned deployment to a completed seabed installation within the same week.

The project is being implemented by Kazakhtelecom and AzerTelecom International through the CaspiLink structure. It is also the first fiber-optic connection to cross the Caspian seabed, rather than a new terrestrial crossing around it. The Kazakh government’s earlier project description framed the line as an alternative data route between Europe and Asia and as a way to improve the resilience of international connectivity.

That description is strategically important, but it should not be confused with an end-to-end route. The cable connects two coastal points. A usable Europe–Asia service still needs transport from Aktau through Kazakhstan, a westbound system from Sumgait through Azerbaijan and the South Caucasus, and onward connectivity to European hubs. The marine milestone is real; the corridor is not yet a finished product.

Capacity is a design number until it is lit

AzerTelecom’s project update states a 380-kilometre route and data-transmission capacity of up to 400 Tbps. A more recent Submarine Networks project update describes capacity above 400 Tbps and says coastal and terrestrial integration work remains under way. Neither current update provides a fiber-pair count, a lit-capacity figure, a product launch date, or a wholesale access model.

Those omissions are not minor technicalities. Design capacity is the potential of the installed system; lit capacity is what the terminal equipment and commercial contracts make available. For a carrier buying protected transit, the relevant questions are how many pairs or wavelengths can be ordered, what increments are offered, where regeneration or grooming occurs, and whether capacity can be protected over a genuinely separate route.

The same distinction applies to the corridor’s much-discussed low latency. A 380-kilometre subsea segment can be engineered for a predictable delay, but a customer does not buy a segment. A Sofia-bound service would also include the terrestrial legs to and across the Caucasus, border crossings, optical nodes, and the final European handoff. Until those pieces are published as an end-to-end service, the cable’s capacity remains an infrastructure option rather than a measurable transit product.

The terrestrial leg is the investment case

The commercial logic is strongest if the Caspian crossing is paired with diverse terrestrial exits. One route could feed west toward Georgia and Türkiye; another could use different border crossings or European interconnection points. The exact design is not stated in the current project announcements, so these should be treated as network-planning options, not as announced routes.

For investors and carriers, this shifts attention from the seabed itself to the assets around it: landing-station backhaul, long-haul fiber, cross-border rights, power and space at optical sites, and the operating procedures used when a segment fails. A new cable can add resilience only when traffic can be moved to it without depending on the same duct, border, power feed or upstream supplier as the primary path.

From construction milestone to carrier-grade service

The project’s public timetable is “fully operational by the end of 2026,” not a specific RFS date. That leaves a set of milestones that the market should watch separately.

1. Acceptance and RFS

The marine installation must be followed by jointing, testing, coastal integration and completion of the terrestrial works. The operator announcement should distinguish construction completion from service availability and publish an RFS window that customers can use for procurement.

2. Capacity and access

The market needs a technical service description: available fiber pairs or wavelengths, initial lit capacity, upgrade path, minimum order size, cross-connect locations, and whether capacity is sold directly by the owners or through a neutral wholesale platform. Without that information, “400 Tbps” is a system specification, not an addressable market.

3. Protection and repair

A cross-Caspian route also needs a repair and maintenance regime that covers the vessel, spares, landing stations and coordination with maritime authorities. The Kazakh government’s current update highlights the logistics and regulatory work required for the marine phase. The next level of disclosure should show how an outage is detected, escalated and isolated across the full Europe-facing path.

What it means for the region

For Bulgaria, the immediate implication is not a new landing station on the Black Sea. It is the possibility of another east–west input into the regional transport and IP-transit stack—provided that the Caucasus-to-Europe terrestrial segments are built, sold and protected independently enough to be useful.

Sofia is already positioned between Central European exchanges, the Balkans, Türkiye and Black Sea routes. The Trans-Caspian system could add value to that position if carriers can buy a defined, protected service from the eastern landing to a European interconnection point, with transparent latency and restoration terms. It could also expose a familiar regional weakness: headline infrastructure is easier to announce than the cross-border operating arrangements that make it dependable.

The right benchmark for the project is therefore not whether 400 Tbps is technically possible. It is whether a carrier in Bulgaria can procure a path that is measurably diverse, commercially available and restorable when a neighboring segment fails. The seabed installation answers the first construction question. The terrestrial network will answer the regional one.

Sources

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