In this paper we will present ultrafast all-optical clock recovery up to 100 Gb/s using two-section gain-coupled DFB lasers. Both the coherent and incoherent schemes will be described. The two-section DFB laser can be used in combination with semiconductor optical amplifier so that clock recovery for both the RZ and NRZ formats can be achieved. For the RZ format, the sensitivity of clock recovery is 50 ?W, the jitter is less than 1 ps at 40 Gb/s. We use parametric amplification for all-optical regeneration. Extinction ratio improvement over 11 dB has been achieved.