Actively mode-locked fiber lasers for high speed telecommunication systems
Lam, Quoc Huy
Date of Issue2009
School of Electrical and Electronic Engineering
Network Technology Research Centre
We propose and develop a novel mathematical series method for analyzing actively mode-locked lasers. Classical analysis methods (self-consistence methods) are very useful in determining the steady-state pulse parameters but don't show the transient evolution of the pulse and the role of amplified stimulated emission (ASE) noise in the process of pulse formation. To overcome this, we propose and derive a set of mathematical series, which are easily calculated from the laser cavity parameters, to trace the evolution of the signal in the laser cavity. Using this approach, we reveal the transient shaping of the pulse from ASE noise under the filtering and modulation effects. We also achieve the steady-state pulse directly from the limit of this transient shaping evolution. Furthermore, we investigate the detuning of actively mode-locked lasers using this method and show that mode-locked pulses are still obtained when the modulation frequency is detuned. The other advantage of our proposed method in comparison with self-consistence analysis methods is that it can be applied to analyze not only laser model without noise but also laser model with ASE noise. We found that minimizing cavity loss and amplifier noise would increase the laser's Signal to Noise Ratio (SNR). On the other hand, the laser's SNR rapidly decreases as the laser is detuned since the pulse experiences higher loss when passing the modulator with position shift. As a result, the locking range is found to be limited by the noise.
DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems