A broad-band digital filtering approach for time-domain Simulation of pulse propagation in optical fiber

A broad-band digital filtering approach for the simulation of pulse propagation in the optical fiber has been developed. Unlike the most popular frequency-domain split-step method, the pulse propagation is realized by letting the signal samples pass through a preextracted digital filter where the convolution is simply made by a series of operations that consist of shift and multiplication only. It also differs from the existing time-domain split-step method in a sense that the digital filter is extracted to match the frequency-domain fiber linear transfer function in the full bandwidth range rather than in a reduced portion. This approach is verified through comparisons made with the conventional frequency-domain split-step method and is applied to the simulation of multiple-channel narrow-pulse propagation over the long-haul fiber. The main advantage brought by this approach lies in that the simulator is fully realized in a "data-flow" fashion; that is, the signal (long sample stream) is treated sample by sample, rather than block (a collection of neighboring samples) by block. Matching the fiber frequency-domain response over the full bandwidth does not require any further reduction on the propagation step since the error can be controlled through the filter length. The authors' preliminary effort on the filter length reduction on a given error reveals that a savings on both memory and computation time is also achievable in comparison with the frequency-domain split-step method.