TEM TE modes (Transverse Electric) have no electric field in the direction of propagation. * TM modes (Transverse Magnetic) have no magnetic field in the direction of propagation. * TEM modes (Transverse ElectroMagnetic) have no electric nor magnetic field in the direction of propagation. * Hybrid modes are those which have both electric and magnetic field components in the direction of propagation

Multi mode fiber are optical fibers which support multiple transverse guided modes for a given optical frequency and polarization. The number of guided modes is determined by the wavelength and the refractive index profile.

one of a set of modes of propagation having the same exponential variation of the field components along the longitudinal axis of a uniform transmission line, but having different configurations in any transverse cross-section

Transverse electromagnetic (TEM) is a mode of propagation where the electric and magnetic field lines are all restricted to directions normal (transverse) to the direction of propagation. Plane waves are TEM, however, we are more interested in what types of transmission lines can support TEM.