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 minimum PM fibers and maintain the polarization of the
incoming light is used in lithium niobate modulators, polarization-sensitive
systems and amplifiers are used.
