Trans-Caspian corridor, part 1: the route from Aktau to Sumgayit and beyond

The Trans-Caspian fibre-optic line that the presidents of Azerbaijan and Kazakhstan inaugurated on 15 October runs for about 380 km along the Caspian seabed between Sumgayit in Azerbaijan and Aktau in Kazakhstan, and has a capacity of more than 400 terabits per second, according to the Azerbaijani presidency's account of the ceremony. This series explains the corridor in five parts: the route, the landing points, the operators, pricing and regulation. Part 1 follows the route.

Under the sea

Laying began in July, when a cable-laying vessel left the port of Baku and started work towards Aktau, The Times of Central Asia reported. The outlet said the armoured cable had been made and tested in China, delivered to the Kazakh port of Kuryk and taken to Baku for installation, and that the route had been chosen to avoid anchorage areas and military exercise zones. By early August the cable had reached the Kazakh coast and crews had begun connecting it to coastal infrastructure, Silk Way TV reported.

On 6 October the Kazakh government said 390 km of cable had been laid between the shores at Sumgayit and Aktau, in its summary of a government session. The presidency gave the line's length as about 380 km; neither document reconciles the two figures.

Where the data goes next

The presidency's account sets out the wider path. The new route "will allow data from China and Central Asia to be transmitted to Europe via Azerbaijan, Kazakhstan and Georgia", and from there onward through the Black Sea or Türkiye, it said. President Kassym-Jomart Tokayev summed up the project in one line: "Yes, this is the Middle Corridor in a digital form."

East of Aktau, the cable meets Kazakhstan's national network. Kazakhtelecom's backbone reaches all of the country's border areas and connects it with China, Russia, Europe and the Central Asian republics, according to the 2024 annual report of the state holding Samruk-Kazyna. A second domestic route is being built: the government said on 6 October that half of the 4,511 km West-East line had been laid and that it aimed to commission the line before the end of the year (same summary).

West of Sumgayit, the documents reviewed for this article do not set out the terrestrial path to the Georgian border or the onward links to Black Sea landings and Turkish networks. Part 2 of the series looks at the landing points.

How the route changed

The crossing has changed partners, capacity and landing point since it was first launched. In November 2019 the prime ministers of the two countries attended a ceremony in Aktau for a line of about 380 to 400 km with a capacity of at least 4 to 6 terabits per second, to be built by Kazakhstan's Transtelecom and KazTransCom with AzerTelecom and to enter service by the end of 2021, The Times of Central Asia reported, citing the Kazakh prime minister's press service. Those targets were missed, the outlet noted in July.

In March 2023 the two operators described a main route of more than 340 km from Aktau to Siyazan in Azerbaijan and a reserve route of about 330 km from Kuryk to Buzovna, near Baku, Capacity reported. That August, Kazakhtelecom told the Kazakhstan Stock Exchange that it held 50 per cent of CASPINET B.V. (KASE notice); Samruk-Kazyna's report describes that company as the project's joint venture with AzerTelecom, each holding half, and says it prepared tender documents and ran a tender for an engineering, procurement and construction contractor in 2024. The Kazakh government's release of 5 August 2026 names the line's builder and operator as CaspiLink B.V., a joint venture of Kazakhtelecom and AzerTelecom International (government release); the documents reviewed do not say whether CaspiLink B.V. and CASPINET B.V. are the same company. In June 2024 Kazakhstan's digital minister said the operators were investing more than $50.6 million, or more than 23 billion tenge, in a 370 km line with a maximum throughput of 400 terabits per second, Report.az reported, citing the government press service; the report placed the line between Aktau and Sumgayit.

Between the 2023 and 2024 descriptions, the Azerbaijani landing moved from Siyazan to Sumgayit. The documents reviewed do not explain the change, and none of them gives a status for the 2023 reserve route.

A southern crossing has been proposed. Turkmenistan's official investment portal describes a 300 km line between Turkmenbashi and Siyazan, to be built by Türkmentelekom and AzerTelecom with a capacity of at least 2 to 4 terabits per second, under an interstate agreement that Azerbaijan approved in April; bne IntelliNews reported the agreement in April 2020. The documents reviewed give no construction start.

Part 2 looks at the landing points at each end, Part 3 at the operators, Part 4 at what capacity costs and Part 5 at the rules that govern transit.