40-wavelength rapidly digitally tunable laser

We present a tunable laser based on an N-1 x N-2 chirped waveguide grating router that has N-1 N-2 wavelengths, accessible in a digitally rapid manner , and only N-1 + N-2 + 1 semiconductor optical amplifiers. By using chirp, the free-spectral range of the router can be significantly less than the ch annel span. The version demonstrated here has N-1 = 5, N-2 = 8, a channel s pacing of 100 GHz, and the router free-spectral range is only 20 channels.