Super-dense WDM transmission technology in the zero-dispersion region employing distributed Raman amplification

This paper describes a practical system design and the transmission performance of high-capacity super-densewavelength-division-multiplexing (SD-WDM) transmission in the zero-dispersion region employing distributed Raman amplification (DRA). By combining several semiconductor laser diodes (LDs) of different wavelengths, gainflattened DRA can be achieved. We quantitatively clarify the relation between the pump power and the maximum input signal power that can be injected into a transmission fiber by taking into account gain saturation due to pump depletion. Based on these analytical results and computer simulations on transmission performance, an SDWDM transmission experiment is conducted. By employing four-wavelength, backward-pumped DRA and forwarderror correction, we successfully demonstrate 1-Tb/s (100 * 10 Gb/s) SD-WDM transmission with 25-GHz channel spacing (0.4-b/s/Hz spectral efficiency) in the C-band (zero-dispersion region) over 4 * 80 km of dispersion-shifted fiber. These results show that DRA is a powerful technology in realizing high-capacity SD-WDM transmission, particularly in the zero-dispersion region.