Submarine Cable Capacity, Ownership and Economics

Submarine cable capacity is described at several layers: design, equipped or lit, activated, and actually used. Ownership, license status, capacity rights, and operational control are distinct. Comparing public figures requires checking fiber pairs, route, equipment assumptions, service readiness, landing access, backhaul, and the rights described.

Capacity is not one number

Submarine cable capacity is often reported as a headline figure, but the meaning depends on context. Three terms are especially important:

  • Design capacity: The planned or theoretical capability of the system under specified technical assumptions.
  • Equipped or lit capacity: The portion of capacity enabled by installed terminal equipment and activated wavelengths or spectrum.
  • Used capacity or traffic carried: The actual traffic being carried at a given time.

A system may be designed for a large future capability but initially lit at a lower level. Another system may have lower design capacity but a higher proportion equipped for current service. Traffic carried will fluctuate with customer demand, routing policies, outages, time of day, and commercial use.

For investors, customers, policymakers, and journalists, the key question is: capacity for what purpose, measured at what layer, and available when?

Fiber pairs, spectrum, and wavelengths

A submarine cable contains optical fibers arranged in fiber pairs. In a conventional pair, one fiber carries signals in one direction and the other carries signals in the opposite direction. The number of fiber pairs is a fundamental design choice, but it does not alone determine capacity.

Each fiber pair supports optical spectrum. Terminal equipment divides usable spectrum into channels, often described as wavelengths. The amount of information carried on each channel depends on modulation, signal quality, spacing, power, distance, and system margin.

Modern coherent transmission uses advanced digital signal processing to encode and recover information from optical signals. Over time, improved modems can support more efficient transmission over the same wet plant, within the limits of the system.

Coherent modems and upgrade paths

A major economic feature of submarine cables is the difference between wet plant and terminal equipment. Wet plant includes the submerged cable, repeaters, branching units, joints, and other undersea components. It is capital-intensive and difficult to replace. Terminal equipment, located on land, can be upgraded more readily.

As coherent modem technology improves, operators may increase equipped capacity without installing a new cable. They may light additional wavelengths, use higher-order modulation where performance permits, optimize spectrum, or deploy new line cards.

However, upgrades are not automatic. The wet plant’s optical characteristics, repeater design, noise performance, available spectrum, power constraints, and required operating margin set boundaries. Longer routes may support different per-wavelength rates from shorter routes. Systems with different fiber types, repeater spacing, or spectrum plans should not be compared solely by headline numbers.

Why capacity announcements are difficult to compare

Two public announcements may use the same unit but mean different things. One may describe design capacity based on future modem assumptions. Another may describe initially lit capacity. A third may describe a specific fiber pair, a segment, a route, or total system capability. Some figures may assume particular modulation formats, spectrum use, or operating margins.

Capacity may also be reported for the whole system, per fiber pair, per wavelength, or per branch. A branching system can make comparison more complex because not all routes may have the same capacity or commercial availability.

Before comparing announcements, ask:

  • Is the figure design, lit, or traffic capacity?
  • Is it per fiber pair, per route, per segment, or total system?
  • What terminal technology is assumed?
  • Is the capacity available at service launch or planned for future upgrades?
  • Does the figure include all branches and landing points?
  • Is terrestrial backhaul available at comparable scale?

Ownership models

A submarine cable may be owned by one entity or by participants in a consortium. FCC licensing records provide concrete examples of consortium ownership and capacity rights, while other records describe privately controlled systems. The legal and commercial documents for a particular system determine the actual arrangement.

Ownership, licensee status, capacity holdings, and operational control are related but distinct. FCC reporting rules have categorized capacity held through an ownership interest, an IRU, or an inter-carrier lease; they also distinguish activated capacity from capacity that is not available for immediate use. Those categories are useful reminders that a headline capacity number does not describe every right or operational state.

IRUs, leases, spectrum, and services

Capacity can be sold, leased, shared, or swapped as fiber, spectrum, or capacity, and providers may offer capacity-management services. An indefeasible right of use, or IRU, is a contractual use right whose exact subject, term, payment, control, and obligations depend on the agreement. An inter-carrier lease is another capacity-holding category used in FCC reporting.

Neither “IRU,” “lease,” “spectrum,” nor another product label alone proves who owns or controls the cable, landing station, terminal equipment, or capacity. Determining those rights requires the governing contracts, licenses, and applicable law. This is a high-level industry explanation, not legal advice; parties should use qualified counsel for a particular transaction.

Route, landing, and operating dependencies

A submarine cable’s usable capacity depends on more than the submerged wet plant. Landing access, terminal equipment, power, terrestrial backhaul, interconnection, maintenance arrangements, spares, and regulatory permissions can affect whether capacity is available to a customer or for restoration.

A route with additional landings or branches may reach more markets, but it also creates additional interfaces, permissions, and operating responsibilities. Those consequences are project-specific; this guide does not assign generalized cost or revenue effects.

The 2025–2026 Submarine Telecoms Industry Report and its release overview provide SubTel Forum’s current house editorial context on system investment, ownership, supply-chain conditions, and bandwidth demand. That analysis is market context, not a legal determination of ownership or capacity rights.

For the engineering sequence behind these dependencies, see how submarine fiber-optic cables work and the submarine cable lifecycle.

Policy and regulatory context

Submarine cable economics are shaped by national licensing, landing rights, security reviews, environmental approvals, and maritime law. International law recognizes important rights and freedoms related to submarine cables, but national implementation varies.

In the United States, the Cable Landing License Act remains the statutory authority. FCC 25-49 adopted an updated licensing framework centered on the 47 CFR 1.70000 series and amended or reserved portions of 1.767. FCC DA 25-934 states that specified rules became effective November 26, 2025, while provisions involving information collections awaited OMB review and later effective-date action. This U.S. framework is not a template for every jurisdiction, and this summary is not legal advice.

Key takeaways

  • Design capacity, lit capacity, and actual traffic are different measures.
  • Fiber-pair count matters, but spectrum, coherent modems, route length, and wet-plant design also determine capacity.
  • Terminal upgrades can increase equipped capacity, but the wet plant sets physical limits.
  • Ownership, licensee status, capacity holdings, and operational control are distinct.
  • IRUs and leases are contractual use rights, not automatically ownership.
  • Landing access, terminal equipment, maintenance, backhaul, and interconnection affect whether capacity is operationally usable.

Sources and further reading

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FAQs

What is design capacity?

Design capacity is the planned or theoretical capability of a submarine cable system under specified technical assumptions. It is not necessarily the amount of capacity installed or carrying traffic.

What is lit capacity?

Lit capacity is the portion of capacity activated with installed terminal equipment and operational wavelengths or spectrum. It can increase over time through upgrades.

Is an IRU the same as ownership?

No. An indefeasible right of use is a contractual right to use specified capacity, fiber, or spectrum under agreed terms. It does not automatically mean ownership of the cable system.

Why are submarine cable capacity announcements hard to compare?

Announcements may refer to design capacity, lit capacity, per-fiber-pair capacity, total system capacity, branch capacity, or future upgrade capability. The assumptions are often different.

Does a capacity product label establish ownership?

No. An IRU, lease, spectrum, fiber, or capacity label describes a commercial arrangement at a high level. Ownership, control, license status, and obligations depend on the governing documents and applicable law.