Where V is the Verdet constant, and B is the static magnetic flux density. The resulting angle of rotation β, is defined by The result of this is a rotation of the plane of polarization, which is linearly proportional to the component of the magnetic field in the direction of propagation. The Faraday effect is a magneto-optical effect where an external magnetic field leads to circular birefringence, and the left and right circularly polarized waves propagate at different velocities. We will also show how this effect can be utilized to create an optical isolator, allowing for transmission of light in only one direction (and preventing unwanted feedback). The latter are used within motor and machine control function blocks.In this example, we will model a Faraday rotator, a device which rotates the polarization of the incident light via the magneto-optical Faraday effect.
![uses for an optical isolator uses for an optical isolator](https://www.designworldonline.com/wp-content/uploads/2012/07/AutomationDirect-Signal-Conditioner-Optical-Isolator.jpg)
With a photodiode as the detector, the output current is proportional to the amount of incident light supplied by the emitter. Unlike a transformer, the opto-isolator allows for DC coupling and generally provides significant protection from serious overvoltage conditions in one circuit affecting the other. When an electrical signal is applied to the input of the opto-isolator, its LED lights, its light sensor then activates, and a corresponding electrical signal is generated at the output.
![uses for an optical isolator uses for an optical isolator](https://i.ebayimg.com/images/g/vrgAAOSwCjpcFxxx/s-l1600.jpg)
![uses for an optical isolator uses for an optical isolator](https://taphome.com/media/1246/DzlikVk9YNXK5dUB8ob3GiW2DcbWGbUOxEFHGoJ5.png)
A common implementation involves a LED and a phototransistor, separated so that light may travel across a barrier but electrical current may not.