@ BLoad
Laser light operates in the 0.4μm to 10μm wavelength range, i would imagine that they would modulate small bands of these wavelengths from one laser source split into the appropriate wavelengths (by the waveguides?) then modulated individualy, then recombined and transmitted to wherever they are going to, then decombined again back into there respective wavlengths where the data is read.
But that's just my guess
