2. Guided transmissions

In the field of optics, unlike in the field of electricity, there are several modes of propagation in the waveguide, depending on its dimensions [E 3 652] :

• When the section of the waveguide is of the order of a few wavelengths, it is referred to as a single-mode waveguide.

• When the cross-section is much larger than the wavelength, it is referred to as a multimode waveguide.

As we have already shown, single-mode optics offer the best performance in terms of bandwidth and linear attenuation,...