Masataka NAKAZAWA

Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan

(Received July 22, 2014; Accepted September 1, 2014)

A compact 1.48 μm InGaAsP laser-diode (LD)-pumped erbium-doped optical fiber amplifier (EDFA) was invented in 1989 and it revolutionized optical communication in combination with a wavelength division multiplexing (WDM) technique. Recently, in addition to the existing single-core EDFA, a multi-core EDFA, which employs space division multiplexing (SDM), was developed to increase transmission capacity even further. The first half of this paper describes the evolution of the EDFA from a single-core to a multi-core device and the second half focuses on related topics in optical communication.

Key words: erbium-doped fiber amplifier, space division multiplexing, multi-core fiber, multi-mode control, multi-level transmission