How effective is Polarization Maintaining (PM) Isolator?

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Polarization
Maintaining Isolator is also known as Fiber Optic Isolator which allows light
to travel only in one direction. For any state of polarization, it minimizes
the back reflection and back scattering in the reverse direction. It is a two
port micro-optic device built with PM panda fiber. Polarization Maintaining
Isolator is used widely in amplifier systems, fiber optic systems, and lasers.
It prevents unwanted feedback into an optical oscillator and the device
operations are dependent on the Faraday’s
effect turn.

 

Faraday
rotator is the main component of the optical isolator. The polarization
dependent isolator mainly consists of 3 parts like an input polarizer, a
Faraday rotator, and an output polarizer. The output polarizer is known as the
analyser. Input polarizer vertically polarizes the light traveling in the
forward direction. Using the analyser, the light traveling in the backward
direction becomes polarized by 45°. The polarization dependent isolators are
mainly used in free space optical systems as the polarization of source is
maintained well by the system.

 

What
are the devices in which the isolator is used?

 

PM
isolator is used in communication systems, polarization maintaining
fiber-optic amplifier and instrumentation applications. Also, the insulating
system is used in CATV Fiberoptic Links, Fiberoptic System Testing and
Fiberoptic LAN System.

 

Here
are the best features of polarization maintaining optical isolator –

 

High
Extinction Ratio

High
Return Loss

High
Isolator

Epoxy
Free Optical Ratio

Low
Insertion Loss

 

The
light traveling in the forward direction is split by the input birefringent
wedge into a vertical component which is called ordinary ray and a horizontal
component is known as extraordinary ray. The rotator rotates both the o-ray and
e-ray by 45°. Again the output birefringent wedge combines the two components.
On either sides of the isolator, collimators are used and the beam is split
& diverged in the isolated direction.

 

There
are now companies who specialize in the manufacturing of the isolators for
various applications. Based on the requirement of applications, isolators are
manufactured precisely. Also, one can get the isolators online and the common
PM Isolators available online are Polarization Maintaining Isolator 1310 &
1480 & 1550nm and Polarization Maintaining Tap Isolator 1310 & 1550nm.