Improved resonance and chirp mechanisms for multigigabit/s push-pull modulated DFB lasers

The internal resonance within a push-pull modulated DFB laser is investigated with numerical and analytical analysis. The classic photon-electron resonance is reduced in amplitude, and the operation of the laser is dominated by a new resonance which is dependant on the mode spacing between the main lasing mode and its nearest side mode. Simulations show that this allows modulation bandwidths well beyond the conventional photon-electron resonance limit. The interaction between the dominant modal resonance and the weaker photon-electron resonance leads to a novel time resolved chirp shape which improves the properties for transmission of a pulse along an optical fibre. This chirp shape can be tailored to further improve transmission properties by controlling the interaction between the resonances. Simulations of the time resolved chirp support published experimental results.