Additive pulse limiting

Actively modelocked lasers are convenient sources of transform-limited pulses which are synchronized to a master clock in optical communications. A convenient source for communications is the erbium fiber laser, which generally has a cavity length 1 m or greater. To achieve a high bit-rate, 1 Gbit/s or greater, with such a long-cavity laser, the modelocking may be done at a harmonic of the laser roundtrip frequency with multiple pulses in the pulse. It has been found in such cases that the pulse energies may fluctuate from pulse to pulse. This is due to the fact that the relaxation time of the gain medium is much longer than the laser roundtrip time, and thus the saturation of the gain medium cannot stabilize against such fluctuations