Optical soliton transmissions at 10 and 20Gbit/s over 1000km with the use of erbium-doped fiber amplifiers are described in detail. For the 10Gbit/s experiment, a bit error rate (BER) of below 110-13 was obtained with 220-1 pseudorandom patterns and the power penalty was less than 0.1dB. In the 20Gbit/s experiment optical multiplexing and demultiplexing techniques were used and a BER of below 110-12 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 over 1 million km at 7.210Gbit/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.

Ac resistivity and power loss values for Mn-Zn ferrite material have been investigated by electrical and magnetic measurements. The ac resistivity shows an inductive dependency on frequency for the low dc resistive samples or for highly dc resistive ones at high temperature, while a capacitive dependency on frequency was observed for the highly resistive materials at the room temperature. These phenomena were interpreted by the dependence of ac resistivity on the dc resistivity, complex permeability and complex permittivity. The dependency of the power losses on the dc resistivity, temperature and frequence were also examined with analysis of power loss term. Dividing the power loss into hysteresis loss and eddy current loss, the frequency dependence of the eddy current loss was found to vary with the magnitude of the dc resistivity as follows: The eddy current loss of low dc resistive materials depends on the dc resistivity. On the other hand, the eddy current loss for high resistive materials is determined by the ac resistivity, contributed from dielectric loss.

A reduction in the intensity deviation of a nine-channel optical frequency comb block (OFCB) is demonstrated, by adopting an asymmetric differential drive method for an InP-based dual drive Mach-Zehnder modulator. The generation of a tailored OFCB with an intensity deviation of less than 0.8dB is confirmed by using the modulator.