All you need to know about polarization maintaining optical circulators

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Since several years, Polarization
Maintaining Optical Circulator has become an important element in the
optical communication system. But these days, its applications have expanded
not only in the telecommunication field but also in imaging and medical field.

 

Polarization Maintaining Optical Circulator

To begin with, let’s discuss what exactly
is an optical circulator?

 

An optical circulator is mainly a multiple
port non-reciprocal passive component. Its function is just similar to that of
a microwave circulator, i.e. to transmit the light wave from one port to other
with maximum intensity. But, at the same time, it also blocks any light
transmission from one port to its previous port. Besides, the entire optical
circulator process is based on the non-reciprocal polarization of the Faraday
Effect.

 

What are the features of Polarization
Maintaining Optical Circulator?

 

There are various features of polarization
maintaining optical circulator. Mentioned below are a few major ones:

 

–   
It has a high stability

 

–   
It has a low insertion loss

 

–   
It has high reliability

 

–   
It has high optical return loss and so on.

 

How can optical circulators be categorized?

 

Optical circulators typically can be
categorized into two main streams namely:

 

–   
Polarization-dependent optical circulator, and

 

–   
Polarization independent optical circulator

 

Polarization-dependent optical circulator
is functional only for a light wave with a specific polarization state. This
type of optical circulator is used only in some of the applications that mainly
include free space communication between crystal sensing and satellites.
Whereas the polarization independent optical circulator is independent of the
polarization state of light. In the ordinary circulators, the polarization is
certainly not maintained, however, there are polarization maintaining optical
circulators available, so they can be used on behalf of it.

 

Besides, they can also be utilized in a
wide variety of applications, but depending on its functionality, optical
circulators may be divided into two groups:

 

–   
Quasi circulator: In this circulator, the light passes through all the
multiple ports, but the light from the last port is lost.

 

–   
Full circulator: In this circulator, the light passes through all the
multiple ports in a full circle.

 

When it comes to circulator’s design, there
are many variations, but, all the non-reciprocal rotation designs certainly
share the same structure with at least three functional elements namely-
non-reciprocal polarization rotation elements, polarization recombining, and
splitting elements, as well as polarization dependent beam steering elements.

 

Finally, we can say that with the large
development of advanced optical networks and elements, the application of
optical circulators are rapidly growing and new and advanced applications and
functionalities are emerging quickly.