Polarization-division multiplexing

A dual polarization system comprises usually two independent transmitters, each of which can be connected by means of waveguide or TEM lines (such as coaxial cables or stripline or quasi-TEM such as microstrip) to a single-polarization antenna for its standard operation.

An ad-hoc component must be therefore introduced in such situations to merge two separate single-polarized signals into one dual-polarized physical interface, namely an ortho-mode transducer (OMT).

Polarization-division multiplexing is typically used together with phase modulation or optical QAM, allowing transmission speeds of 100 Gbit/s or more over a single wavelength.

Sets of PDM wavelength signals can then be carried over wavelength-division multiplexing infrastructure, potentially substantially expanding its capacity.

[1] The major problem with the practical use of PDM over fiber-optic transmission systems are the drifts in polarization state that occur continuously over time due to physical changes in the fibre environment.

Over a long-distance system, these drifts accumulate progressively without limit, resulting in rapid and erratic rotation of the polarized light's Jones vector over the entire Poincaré sphere.

[2] Companies working on commercial PDM technology include Alcatel-Lucent, Ciena, Cisco Systems, Huawei and Infinera.