The emergence of practical optical amplifiers greatly simplifies the construction of ultra-high-speed transmission systems that are very flexible.Erbium-doped fiber amplifiers (EDFAs) are characterized by their high gain,high output power,ultra-broadband and low noise characteristics.They are encouraging the development of a new generation of ultra-high speed IM/DD (Intensity modulation and direct detection) systems.Recent experimental results are summarized to confirm that EDFAs can up-grade existing systems to longer span systems,bit-rate flexible optical systems,and ultra-high-speed systems with optical equalization.New experimental results on quantum-effect devices at 1.3 μm are reported.The newly developed high-speed technologies can be applied not only for trunk transmission but also short-distance data links.
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