polarization division multiplexing (photonics) (PDM)

Polarization Division Multiplexing (PDM) is an optical multiplexing method used in optical transmission systems in which the available transmission channel is shared between several users.

In polarization division multiplexing, the optical transmission channels are assigned to different polarization planes. One light signal is modulated with the signal from one channel and transmitted in one plane of polarization, and a second, which carries the information from a second channel, is transmitted in a second plane. The light signals have the same wavelengths, but differ in the plane of polarization rotated by 90°.