Polarization-maintaining/PM connector is an optical connector application that polarization need to be maintained, widely applications including Fiber Optical Sensor, Interferometry, Planar Lightwave Circuit, Coherent optical transmission and long-distance bidirectional optical transmission systems.

Polarization-maintaining/PM fiber is a special type of single-mode fiber. Ordinary single-mode fibers transmits unpolarized light, and Polarization-maintaining/PM fiber can only transmits certain direction polarized light.