COLUMBUS III is a 9,900 km transatlantic submarine cable linking the US, Portugal, Spain and Italy. COLUMBUS III was ready for service in December 1999, with 2 fiber pairs and a design capacity of 20 Gbps.

The Columbus III consortium comprises:

• AT&T,
• Verizon,
• Telxius,
• Portugal Telecom,
• Tata Communications,
• Telecom Italia Sparkle,
• Telkom South Africa,
• Telecom Argentina,
• Instituto Costarricense de Electricidad,
• Embratel,
• Cyta,
• CANTV,
• Ukrtelecom

The Columbus III cable lands at:

• T1: Hollywood, FL, United States
• T2: Ponta Delgada, Azores Island, Portugal
• T3: Carcavelos, Lisboa, Portugal
• T4: Conil, Spain
• T5: Mazara del Vallo, Sicily, Italy

The COLUMBUS-III cable system consists of five segments, S1, S2, S3, S4, and S5, with two optical fiber pairs per segment, initially designed to operate at 2.5 Gbps per wavelength per fiber pair in a trunk and branch structure configured as a collapsed ring. COLUMBUS-III was initially be configured with two wavelengths, designed to support up to eight wavelengths per fiber pair. The capacity of each fiber pair comprises thirty-two Basic System Modules (BSM), with each BSM containing 63 Minimum Investment Units (MIUs). Each fiber pair was equipped at the outset with a capacity of 1008 MIUs.

The COLUMBUS-III cable system also has four other terminal segments: Segment A, B, C and D, as shown in the figure below: 

In 2009, the Columbus III consortium selected Xtera to upgrade the system capacity to 160 Gbps, with Xtera’s advanced 20 Gbps Differential Phase Shift Key (DPSK) Submarine Line Terminal Equipment (SLTE).