# Which wave is widely used in waveguides?

I've studied that the rectangular waveguides are widely used because they have less cut-off frequency and as we know that the cut-off frequency is one of the major factors for waveguides. The article I've read has mentioned TE wave!

Question: Which wave is more commonly used in a waveguide?

or

My question is wrong!? It can be that they both are used in particular situations.

• as hyportnex said, it boils down to your applicaiton. But ideal would be to use the fundamental mode, which tends to be either a TE or TEM wave depending on the gemetry. – DakkVader Sep 9 '18 at 12:56

It depends on the shape. For a homogeneous rectangular waveguide the 1st mode is the $TE_{10}$ but for a circular guide is $TE_{11}$. For a coaxial guide the fundamental mode is TEM but if it is inhomogeneously filled such as a microstrip line where propagation is partly in air and partly in the dielectric substrate the mode is essentially a hybrid of TEM and TE. In dielectric guides that are popular in fiber optics the propagating modes are all hybrid modes, as well. In general, the closer the frequency is to that of the cutoff the more the mode approximates a pure TEM, TE or TM, respectively. Away from the cutoff there are no pure TEM, TE or TM modes unless the guide is filled homonegeneously.