40-Wavelength Rapidly Digitally Tunable Laser

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