Junior: a short-haul submarine cable connecting Rio de Janeiro and Santos
Junior is a submarine cable owned by Google that spans 390 kilometers, connecting Rio de Janeiro and Santos, both located in Brazil. It is listed as in service and was recorded as ready for service (RFS) in 2018 according to GeoCables data. This cable is notable for its relatively short length compared to many transoceanic systems and its focus on linking two major urban centers in Brazil.
What stands out about Junior is the lack of publicly disclosed technical details, such as its design capacity, fiber pair count, supplier, and specific technology. This absence of information limits the ability to fully assess its role in the broader telecommunications network between these cities. Additionally, Junior operates in a corridor with multiple alternative cables, raising questions about its unique contribution to redundancy or capacity.
Quick facts
| Name | Junior |
| Length | 390 km |
| Ready for Service (RFS) | 2018 (GeoCables database) |
| Owners | Google |
| Status | In service |
| Design Capacity | Not disclosed |
| Fiber Pairs | Not disclosed |
| Supplier | Not disclosed |
| Technology | Not disclosed |
| Landing Points | Rio de Janeiro (Brazil), Santos (Brazil) |
Route
Junior connects Rio de Janeiro and Santos, two key coastal cities in Brazil. Rio de Janeiro is a major economic hub and cultural center, while Santos is home to the largest port in Latin America, making it a critical node for trade and logistics. The cable's route is entirely within Brazilian territorial waters, which simplifies regulatory considerations compared to international cables.
Both landing points are well-served by other submarine cables. Rio de Janeiro hosts seven other systems, including AMX-1,
Brazilian Festoon,
BRUSA,
GlobeNet,
Malbec,
South America-1 (SAm-1), and
South American Crossing (SAC). Santos is connected by
Monet, South America-1 (SAm-1), South American Crossing (SAC), and
Tannat. These overlapping systems provide redundancy and additional capacity for telecommunications between these cities.
Why it was built and what it carries
Junior was likely built to enhance connectivity between Rio de Janeiro and Santos, supporting Google's operations and potentially improving latency for its services in Brazil. Given Google's ownership, the cable may primarily serve the company's internal data traffic, such as cloud services, search, and video streaming. However, without public disclosures about its capacity or utilization, this remains speculative.
The corridor between Rio de Janeiro and Santos is already served by other cables, including South America-1 (SAm-1) and South American Crossing (SAC). Junior may have been designed to provide additional redundancy or to ensure dedicated bandwidth for Google's needs.
History: what can be established
GeoCables records Junior as ready for service in 2018, and it is listed as in service. No conflicting RFS dates have been identified in industry sources, which suggests that the 2018 date is reliable. However, the absence of detailed public announcements or technical specifications makes it difficult to trace the cable's development timeline, supplier involvement, or initial testing phases.
Capacity and technology
Publicly available information does not disclose Junior's design capacity, fiber pair count, or the specific technology employed. Without operator documentation, attributing these details would be speculative. Given Google's ownership, it is reasonable to assume the cable employs modern optical transmission technologies, but the exact configuration remains unknown.
Latency: the physics
The theoretical one-way latency for light propagation over Junior's 390 km wet segment is approximately 1.9 milliseconds, with a round-trip time (RTT) floor of 3.8 milliseconds. These calculations assume light travels through fiber at speeds between 200,000 and 204,000 km/s. Real-world latency would be higher due to additional factors such as land-based tails, terminal equipment delays, and routing inefficiencies.
No live latency measurements are currently available for Junior, so its real-world performance cannot be assessed.
Redundancy: what happens if it breaks
If Junior were to experience a fault, alternative cables in the same corridor, such as South America-1 (SAm-1) and South American Crossing (SAC), could provide redundancy. Both Rio de Janeiro and Santos are well-connected landing points, hosting multiple cables that could absorb traffic in the event of an outage.
Standard industry practices for submarine cable repair include deploying specialized cable ships to locate and fix faults. Given its short length and proximity to shore, Junior would likely be relatively straightforward to repair compared to longer, deep-sea cables.
Bottom line
- Junior is a 390 km submarine cable owned by Google, connecting Rio de Janeiro and Santos in Brazil.
- It was recorded as ready for service in 2018, with no conflicting dates identified.
- Key technical details, such as design capacity and fiber pair count, are not publicly disclosed.
- Theoretical latency over the wet segment is approximately 3.8 ms RTT, though real-world performance would be higher.
- Redundancy is provided by other cables in the corridor, including South America-1 (SAm-1) and South American Crossing (SAC).