Cascaded Fabry-Pérot lasers for coherent expansion of wavelength tunable gain switched comb

We propose a simple potentially integrable configuration for expanding a wavelength tunable comb by cascading gain switched Fabry-Pérot lasers. A 10GHz spaced comb, exhibiting 13 coherent low-linewidth tones within a 3 dB window, and tunable over 20 nm is demonstrated.