COLUMBUS II is an optical, repeatered, transatlantic telephone cable. It is approximately 12,102 km (7,520 mi; 6,535 nmi) in length. It entered into commercial service in 1994.[1] The system, along with the Americas cable, was the first to use the Erbium-doped fiber amplifier (EDFA) as its optical amplifier repeaters.[2] In 2009, the transatlantic section was retired, and as of 2023, only the Columbus-II-B section remains in use and has been upgraded. [3]