What are Polarization Maintaining Fibers? Fiber Optics Tutorial Series 6

:: What is polarization?

Flashing waves consist of oscillating electric and magnetic fields. These two fields are perpendicular to each other and to the direction of glassy 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 analogue to everyone other, we call this glossy linearly polarized.

:: Polarization's fallout on optical fibers

Polarization does not really matter in multimode fibers but it can be crucial in unmarried mode fibers especially for long distance and high speed rate fibre communications. Why? Let me explain it below.

Technically speaking, single funds fibers truly have two modes travelling in it. These two modes accept orthogonal polarization and flawless single mode 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 excursion along the fiber at slightly different speeds. The event is called PMD (polarization mode dispersion). The slight speed difference can cause problems in alpine speed fiber optic links such as 10Gbit/s and 40Gbit/s.

:: Polarization maintaining fibers come to the rescue!

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

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

PM fibers can transmit brilliant in a single polarization if 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 rarely used for enduring distance transmission because of their expensive price and higher attenuation than single mode fiber. They are commonly used for telecommunication applications, fiber optic sensing and interferometry.


Colin Yao is the sales director at Fiber Optics For Sale Co. and an expert on fiber optic technologies and products. Be taught much more about polarization maintaining fibers, PM fiber and Panda PM fiber on Fiber Optics For Sale Co. web site.

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