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What is an Optical Isolator?

11/18/2013 5:07:22 PM | by Anonymous


An optical isolator is an object that allows a beam of light to stream through a single one way direction. At the same time, it prevents the light from going back in the opposite direction. The device would usually include a polarizer together with the faraday rotator. The faraday rotator is a piece of crystalline that rotates on the plane of polarization of the light beam. This occurs whenever a magnetic field is applied onto the rotator from the outside. After which, the output polarizer will reflect the light at 45 degrees before leaving.


Similarly, the input polarizer passes light streams into the isolator would allow for the light to pass through at the exact angle by which it has entered. This is done before it is altered by the Faraday Effect. These are usually common set ups with both optical and laser communication systems.


The direction of which the plane of polarization rotates is usually controlled by how affected the light beam would be by the faraday rotator. The change in state of the light can be controlled with a magnet as well. In the optical communication system, the signals are usually electric and are first converted into light before it is allowed to enter the optical isolator. Following suit, they are then transmitted in the direction of a single stream. This is done so to prevent the portion of light from being reflected in the backward direction. When it is reflected back, it would cause the alteration of the frequency of the laser. This can cause potential issues such as rendering the system ineffective or transmitting signals that are unable to convey necessary information from a communication system. Data that are in the fiber network would also be altered. This would lead to the data being unreadable and corrupted once it reaches the hands of the receivers who then reprocess the signals back into electric signals.


Along side many other types of components, the optical isolator is also used. These components are such as the optical amplifiers, depolarizers and combiners. They are used to fully utilize the light in the communication or measurement system. Each of them will rotate the plane of polarization towards the 45 degrees mark while passing through the output polarizer followed by the magnetic field. All of which are conducted before the light is reflected at a 90 degrees.


The optical diode can also be referred as a device that has the abilities in directing light in the same way. This is done to prevent the light from going back and being reflected back through the fiber after the laser beam. They are used as a source of light that passes through the coupling lens and back into the fiber optic wire.


In order to use the optical and laser communication systems, the isolators are also used on circuits with the purpose of isolation. This acts as a form of protection against excessively high voltages. At the same time, noise levels are also reduced in the process. This allows for accurate measurements and the optimization of quality of data. The optical isolator is usually small and is mounted directly in the light path onto the circuit board.


It may first seem that within the first glance, the device would allow light to flow in a single direction violating the law of kirchoff’s followed by the second law that incorporates thermodynamics. This is all done to permit light energy to flow from a cold to hot object which in the end blocks it in the other direction. The violation is however avoided due to the isolator absorbing light that comes from the hot object. Eventually, it will reradiate it onto the cold one instead of reflecting it. Attempts of rerouting the photons back to the sources they come from are also inevitable.


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