4 × 20 Gb/s L-band NRZ signal transmission through a metro-scaled NZD fiber link

We describe an L-band WDM error-free transmission over 50 km of nonzero dispersion-shifted fiber, at a per-channel rate of 20 Gb/s. By allocating an equally spaced 4-channel optical stream close to the fiber zero-dispersion wavelength, and transmitting them in a linear regime, no dispersion-compensating module is required and no four-wave mixing effect is observed. Except for the lithium niobate modulator and the O/E receiver bandwidths, all system elements have been previously specified for 10 Gb/s L-band WDM transmissions. The experimental results demonstrate the feasibility of upgrading a system capacity by combining the L-band amplification with a dispersion shifted fiber, and a linear-regime transmission at a bit-rate of 20 Gb/s, which is less technologically restringing and complex than 40 Gb/s. The strategy of reducing the need for new components and reusing the legacy equipment may represent a significant cost impact in a metro-scaled system upgrade.