Transmission performance improvement of semiconductor lasers by hybrid modulation scheme

We propose a hybrid modulation scheme which has a wider 3-dB bandwidth and higher dispersion tolerance compared with a direct current modulation (DM) scheme. Frequency responses and eye diagrams are calculated by using rate equations. The calculated frequency response shows that the hybrid modulation scheme improves modulation sensitivity degradation at a high-frequency region and enhances 3-dB bandwidth of a semiconductor laser. Comparison of the eye diagrams between DM and hybrid modulation schemes shows that the hybrid modulation scheme has a good dispersion tolerance compared with the DM scheme thanks to its negative chirp property.