Southern Caribbean Fiber

Southern Caribbean Fiber: connecting island nations

The Southern Caribbean Fiber (SCF) is a submarine telecommunications cable spanning approximately 3,000 kilometers. Owned by Digicel and listed as in service since 2006, it connects multiple islands in the Caribbean region, as well as landing in San Juan (United States) and St. Croix (Virgin Islands (U.S.)). The cable plays a role in linking smaller island nations to larger hubs, facilitating international connectivity across the region.

What makes SCF interesting is its extensive reach across the Caribbean, touching 16 landing points. However, publicly disclosed information about its design capacity, fiber pairs, and technology is scarce, leaving questions about its technical specifications unanswered. Additionally, latency measurements from remote probes reveal artifacts and higher-than-expected values, underscoring the complexities of interpreting real-world performance data.

Quick facts

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Route

The Southern Caribbean Fiber connects 16 landing points across the Caribbean, spanning territories such as Guadeloupe, Saint Kitts and Nevis, Montserrat, Dominica, Trinidad and Tobago, Antigua and Barbuda, Saint Barthélemy, Saint Vincent and the Grenadines, Martinique, Barbados, Grenada, Saint Lucia, Saint Martin, the United States, and the Virgin Islands (U.S.). This broad coverage makes it one of the region's key cables for inter-island communication and international connectivity.

Several landing points are shared with other submarine cables, such as Baillif (Global Caribbean Network), Basseterre (Antigua-St.Kitts, Saba, Statia Cable System), and Chaguaramas (Deep Blue One, Eastern Caribbean Fiber System, EC Link, Suriname-Guyana Submarine Cable System). These overlaps provide redundancy options in case of disruptions.

Why it was built and what it carries

The SCF was built to enhance connectivity among Caribbean nations, many of which are geographically isolated and depend heavily on submarine cables for international communication. By linking smaller island nations to larger hubs like San Juan and St. Croix, the cable facilitates data, voice, and internet traffic across the region. Its role is particularly significant for countries with limited local infrastructure or alternative connectivity options.

Given the lack of publicly disclosed data on its design capacity or technology, it is difficult to gauge the specific scale of traffic it handles. However, its strategic placement suggests it is an important asset for Digicel's regional operations.

History: what can be established

According to GeoCables records, the Southern Caribbean Fiber became ready for service in 2006. This date aligns with the broader trend of submarine cable deployments in the mid-2000s, driven by increasing demand for broadband connectivity in the Caribbean. No conflicting dates have surfaced from other industry sources, leaving the 2006 RFS year uncontested.

Digicel's ownership of the cable aligns with its role as a major telecommunications provider in the Caribbean. However, details about the cable's supplier, construction process, and initial deployment remain undisclosed in public sources.

Capacity and technology

Publicly available information does not provide details about the cable's design capacity, the number of fiber pairs, or the specific technology employed. Without operator documentation, it is impossible to make reliable statements about these aspects. However, given the cable's operational status and regional importance, it is reasonable to assume it employs standard industry practices for submarine cable technology, such as optical amplification and wavelength-division multiplexing.

Latency: the physics

The computed one-way light propagation latency for the 3,000 km wet segment of the SCF is approximately 14.7 milliseconds, with a theoretical round-trip time (RTT) floor of 29.4 milliseconds. These values represent the physical limits of light traveling through fiber, assuming speeds between 200,000 and 204,000 km/s.

Live latency measurements from remote probes show significantly higher RTTs, reflecting the impact of land tails, terminal equipment, and routing. For example, Chaguaramas to San Juan measurements average 114.9 ms, far above the theoretical floor. Notably, a minimum RTT of 1.5 ms was recorded for San Juan to Chaguaramas, but this is below the physical floor and must be attributed to measurement artifacts, such as rate-limited ICMP replies. Analysts should treat such values with caution and avoid quoting them as real path latency.

Redundancy: what happens if it breaks

In the event of a disruption to the SCF, redundancy is available through overlapping cables at many landing points. For example, Chaguaramas connects to Deep Blue One, ECFS, EC Link, and SG-SCS, while San Juan serves as a hub for multiple cables, including AMX-1, BRUSA, PCCS, and SAm-1. These alternatives provide resilience for regional and international traffic.

Standard industry practices for submarine cable repair include deploying specialized cable ships to locate and fix faults, which may involve splicing or replacing damaged segments. The repair process can take weeks, depending on the location and severity of the fault.

Bottom line

• The Southern Caribbean Fiber spans 3,000 km and connects 16 landing points across the Caribbean and the United States.
• Owned by Digicel, it has been in service since 2006, with no publicly disclosed data on design capacity, fiber pairs, or technology.
• Computed latency values suggest a theoretical RTT floor of 29.4 ms, but real-world measurements show higher values due to additional factors.
• Redundancy is available through overlapping cables at many landing points, ensuring resilience in case of disruptions.