The dynamic characteristics of an ultra-long semiconductor optical amplifier (UL-SOA) with a length of 4 mm are investigated experimentally. An optically clocked technique is applied for suppressing the patterning effects in an SOA and for exploiting effectively the fast intra-band effects. The gain dynamic in the UL-SOAs is here stabilised by a sinusoidal optical clock signal which is additionally injected into the device, bit interleaved with a PRBS data signal. The optimal operation condition of the novel scheme concerning power levels of the RZ data signal and clock signal are analysed in detail at 40 Gbit/s. We use the ultra-fast nonlinearities in the UL-SOAs for regenerating of a 40 Gbit/s data signal in amplitude, time and pulse shape. The 40 GHz recovered clock signal in the optically clocked 3R regenerator is generated by a self-pulsating three section DFB laser. An excellent regenerative performance even for strong degraded data signals is demonstrated.