Predicted redshift distribution of auto and cross power spectra at large (ℓ = 1000, left) and small scale (Poisson level). We focus on three frequencies: 857 GHz (350 μm), 545 GHz (550 μm), and 217 GHz (1382 μm) to illustrate the difference between cross spectrum between two distant wavelengths and the auto-spectrum at an intermediate wavelength. The flux density cuts are the same as previously (see Sect. 6 and Fig. 7).