A NEW DESIGN ARRANGEMENT OF TRANSMISSION FIBER DISPERSION FOR SUPPRESSING NONLINEAR DEGRADATION IN LONG-DISTANCE OPTICAL-TRANSMISSION SYSTEMS WITH OPTICAL REPEATER AMPLIFIERS

The invention of the erbium-doped fiber amplifier has opened the possi bility of constructing long-distance optical transmission systems with 1.5-mum zero-dispersion wavelength shifted fibers. In such systems, n onlinear degradation due to four-wave mixing and self-phase modulation strictly limits the total span of systems and the length of the optic al repeater spacing. There are proposals to use slightly normal group velocity dispersion fibers (D < 0) through the whole system or to arra nge the various sections of different dispersion fiber in the cable fo r suppressing these nonlinearities [1]. However, these strategies are not so easily applied in real systems. In this paper, the authors have proposed a new arrangement of transmission fiber dispersion which eas ily suppresses these nonlinearities so as to expand the total span of the system or to increase the repeater spacings. The feasibility of th e proposal has been experimentally confirmed.