What are Polarization Maintaining Fibers? Fibre Optics Tutorial Series 6

:: What is polarization?

Light waves consist of oscillating electric and magnetic fields. These two fields are perpendicular to everyone other and to the course of glowing traveling. We call the electric field plane as the light's polarization.

Sunlight and many other common light is made of many light waves, each with their electric and magnetic fields oriented randomly. If all waves' electric fields were aligned equal to each other, we call this light linearly polarized.

:: Polarization's effect on optical fibers

Polarization does not really matter in multimode fibers on the contrary it can be crucial in single funds fibers especially for long distance and high speed rate fiber communications. Why? Let me explain it below.

Technically speaking, single income fibers actually have two modes traveling in it. These two modes chalk up orthogonal polarization and finished single resources fibers cannot differentiate between them. These two modes are functionally identical and light energy can shift easily between these two polarization modes.

However, fiber's geometry is not perfect. As a result, these two modes actually travel along the fiber at slightly different speeds. The eventuality is called PMD (polarization method dispersion). The slight speed difference can cause problems in giant speed fiber optic links such as 10Gbit/s and 40Gbit/s.

:: Polarization maintaining fibers come to the rescue!

Polarization maintaining fibers are special kinds of single mode fibers, they are also commonly called PM fibers or Panda PM fibers.

PM fibers have built-in asymmetry which is again called birefringence. The refractive index of PM fiber differs for the two polarizations and this effect prevent light energy from coupling between two polarizations.

PM fibers can transmit light in a single polarization provided the input light polarization is aligned to one of its two birefringence axes. And that is why they are called polarization maintaining fibers.

:: The applications of polarization maintaining fibers

PM fibers are infrequently used for long distance transmission because of their expensive valuation and higher attenuation than single mode fiber. They are commonly used for telecommunication applications, fiber optic sensing and interferometry.


Colin Yao is the sales employer at Fiber Optics For Sale Co. and an expert on fiber optic technologies and products. Learn even more about polarization maintaining fibers, PM fiber and Panda PM fiber on Fiber Optics For Sale Co. lattice site.

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