Periodic allocation of a set of unequally spaced channels for WDM systems adopting dispersion-shifted fibers

To enhance the upgradability of the unequally spaced channel allocation (USCA), we propose a periodic allocation of an USCA set for optical wavelength-division multiplexing systems adopting dispersion-shifted fibers. Contrary to USCA, the channel number can be increased smoothly without changing old channel locations. The average optical bandwidth per channel is essentially fixed even though the channel number is increased indefinitely.