Optical soliton communication system using erbium-doped fiber amplifiers

Ultra-high speed optical soliton transmissions over 1000 km achieved through the use of lumped erbium-doped fiber amplifiers are described in detail. In a 10 Gbit/s experiment, a bit error rate (BER) of below 1 × 10⁻¹³ was obtained with 2²⁰−1 pseudorandom patterns and the power penalty was less than 0.1 dB. In a 20 Gbit/s experiment optical multiplexing and demultiplexing techniques were used and a BER of below 1 × 10⁻¹² was obtained with 2²³−1 pseudorandom patterns under a penalty-free condition. A new technique for sending soliton pulses over ultralong distances is presented, which incorporates synchronous shaping and retiming using a high-speed optical modulator. Some experimental results for a transmission over 1 million km at 7.2 ∼ 10 Gbit/s are described. This technique enables us to overcome the Gordon-Haus limit, the accumulation of amplified spontaneous emission (ASE), and the effect of interaction forces between adjacent solitons. It is also shown by computer runs and a simple analysis that a one hundred million km soliton transmission is possible by means of soliton transmission controls in the time and frequency domains. This means that limit-free transmission is possible.