What is the application of Optical Circulator?

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An optical circulator is a special
fiber-optic component that can be used to separate optical signals that travel
in opposite directions in an optical fiber, analogous to the operation of an
electronic circulator. An optical circulator is a three-port device designed
such that light entering any port exits from the next. This means that if light
enters port 1 it is emitted from port 2, but if some of the emitted light is
reflected back to the circulator, it does not come out of port 1, but instead
exits from port 3.

 

Fiber
optic circulators are non-reciprocal optics,
which means that changes in the properties of light passing through the device
are not reversed when the light passes through in the opposite direction. This
can only happen when the symmetry of the system is broken, for example by an
external magnetic field. A Faraday rotator is another example of a non-reciprocal
optical device.

 

The Configuration of optical circulator

 

As shown in Fig.2(a), an optical circulator
typically has three input or output ports. The signal light input into the port
1 is output from the port 2. The signal light input into the port 2 is output
from the port 3. The optical circulator is often used with adding an FBG at the
port 2 as shown in Fig.2(b). For reference, a composition of optical circulator
is shown in Fig.3.

 

The application of Optical Circulator

 

An optical circulator is frequently used
for an optical time domain reflectometer (OTDR), an optical add-drop
multiplexer (OADM) and a dense wavelength devision multiplexing (DWDM) network
using an FBG, and a pulse stretcher, a pulse compressor, and a disprersion
compensator using a chirped FBG. Optical Circulators can be used to achieve
bi-directional transmission over a single fiber. Because of its high isolation
of the input and reflected optical powers and its low insertion loss, optical
circulators are widely used in advanced communication systems and fiber-optic
sensor applications.