Bit-error-rate characterization of IM-DD ultralong-distance optical communication systems with Er-doped fiber amplifiers using a recirculating loop

The authors have evaluated the bit error-rate characteristics of the IM-DD ultralong-distance optical communication systems employing Er doped fiber amplifiers. A 2.5- and 5-Gb/s IM-DD nonreturn-to-zero signal was analyzed by recirculating-loop experiments. They used a fiber loop of four Er-doped fiber amplifiers and three spans of dispersion-shifted single-mode fibers for the experiments. A 16,000-km transmission at 2.5 Gb/s and an 11,000-km transmission at 5 Gb/s were successfully achieved. The allowable wavelength-tunable range of the optical transmitter for the 9000-km transmission was also measured at the bit rate of 5 Gb/s. The experimental results show the possibilities and limitations of transoceanic optical communication systems using Er-doped fiber amplifier repeaters.< >