Polarization
A type of electromagnetic wave is Light. Denoted by E, It consists of oscillating electrical fields, and denoted by B, magnetic fields. By studying its electrical field E, Its properties can be described although, in terms of the magnetic field, we could just as well describe light and its effects. The polarization maintaining splitter is very useful.
Light-is-a-electromagnetic-wave and in many directions, Light waves can vibrate. Those that are vibrating in a single plane and one direction such as up and down are known as polarized light. Those that are vibrating in more than one plane and more than one direction such as both left/right and up/down are called unpolarized light.
Using a polarization filter is the most common method of achieving single polarization. Capable of blocking one of the two planes of vibration of an electromagnetic wave, Polarization filters are made of special materials.
Polarization maintaining fiber
A special type of single-mode fiber is Polarization maintaining fiber (PM Fiber). Normal single-mode fibers can carry randomly polarized light. However, to propagate only one polarization of the input light, PM fiber is designed.
With no or little cross-coupling of optical power between the polarization modes, the polarization of linearly-polarized light waves launched into the fiber is maintained during propagation in polarization-maintaining fiber. For some fiber optic components such as external modulators and polarization maintaining isolator that require a polarized light input, this polarization-maintaining feature is extremely crucial.
By inducing stresses in the material itself, this characteristic is achieved during the manufacturing process. Circular polarization-maintaining fiber and linear polarization-maintaining fiber are the two categories of polarization maintaining fiber (PMF) available.
Polarization maintaining fibers applications
In special applications, such as slab dielectric waveguides, interferometry, and fiber optic sensing, PM optical fibers are used in long-distance bidirectional optical transmission systems, polarization maintaining patch cable or coherent optical transmission systems, PM fibers are expected to be used.
Where the polarization plane of the optical signal is important, they may also be used in transmission applications such as coupling for optical-electrical integrated circuits and transmission lines for optical sensors. To keep cross-coupling between polarization modes at a minimum PM fibers and maintain the polarization of the incoming light are used in lithium niobate modulators, polarization-sensitive systems, and amplifiers are used.
