Optical Isolator is an optical analogue of an electrical diode which allows light transmission in only one direction. Typically, optical isolators are used in free space optical applications where parasitic light from back reflections must be eliminated or minimized. Principally, optical isolator contains a Faraday rotator which produces rotation in the polarization state by the Faraday Effect. There are two types of isolators - polarization dependent and independent. Looking at their construction, the optical isolator consists of two polarization elements (a polarizer and an analyser having a 45° differential in the direction of their light transmission axes), and of a 45° Faraday rotator interposed between the polarization elements.