Methodology of Unequally Spaced Frequency Allocation for WDM Transmission Systems Using Typical Dispersion-Shifted Fiber Cable

The transmission performance of WDM transmission systems is influenced by many effects according to the type of optical fiber employed in the system. Japanese highspeed transmission systems use dispersion-shifted fiber (DSF). It is well known that the transmission distance of WDM systems employing DSF is restricted by fiber four-wave mixing (FWM). Unequally spaced channel allocation (USCA) was proposed to mitigate the FWM effect. However, if no FWM light is allowed to fall on any optical channel, the number of channels is limited. This paper proposes a new method to extend the number of USCA channels to more than 16 under the optical bandwidth limitation. This method determines channel allocation by considering the distribution of the zero-dispersion wavelength of the optical fiber. The transmission performance of a WDM transmission system employing the proposed USCA methodology is clarified by numerical simulation to confirm that the optical bandwidth requirements can be reduced without degrading transmission performance. As a result, for 16 × 2.5 Gbit/s, if the fiber input power ranges from −3 dBm/ch to 3 dBm/ch, the achievable transmission distance is 700 km; the fluctuation in zero-dispersion wavelength is assumed to have the standard deviation of 5 nm. For 16×10 Gbit/s, if the fiber input power ranges from 0 dBm/ch to 3 dBm/ch, the achievable transmission distance is 400 km. key words: WDM, DSF, FWM, unequally spaced channel allo-