Comment on Observation of dark pulse in a dispersion-managed fiber ring laser

A recent communication [Opt. Commun. doi:10.1016/j.optcom.2010.06.076 (2010)] presents experimental results in which dark pulses are observed in a dispersion-managed (DM) net-anomalous dispersion fiber laser. Disagreement on the formation mechanism proposed in this communication, we would like to indicate a more accurate explanation in order to clarify some potential misunderstanding on dark pulses in fiber lasers.