In an optical fiber transmission line, wich employs optical fiber amplifiers to compensate the transmission loss and is composed of alternatively allocated negative dispersion fibers and positive dispersion fibers or dispersion compensators, making the efficient dispersion of the transmission line properly higher than the theoretical value corresponding to the average soliton and using phase conjugstors periodically along the line, the interaction among the solitons can be reducted effectively under the amplifier spacing is increased as same as in the ordinary linear optical fiber communication. The soliton transmission with pulse-duty-ratio of 1/2, amplifier spacing of 100 km and transmission distance of 6000 km or more is demonstrated numerically.