Polarization independent isolator Figure 3: Polarization independent isolator Hence the angle of polarization will lead to a loss. In optical fibre systems, the polarization direction is typically dispersed in non polarization maintaining systems. This is because the polarization of the source is typically maintained by the system.
MICRO FARADAY ISOLATOR FREE
Polarization dependent isolators are typically used in free space optical systems. The Faraday rotator is chosen to give a 45° rotation. For a polarization dependent isolator, the angle between the polarizer and the analyzer, β \beta, is set to 45°. Since the polarizer is vertically aligned, the light will be extinguished.įigure 2 shows a Faraday rotator with an input polarizer, and an output analyzer. This means the light is polarized horizontally (the direction of rotation is not sensitive to the direction of propagation). The Faraday rotator will again rotate the polarization by 45°. Light traveling in the backward direction becomes polarized at 45° by the analyzer.
The analyzer then enables the light to be transmitted through the isolator. The Faraday rotator will rotate the polarization by 45°. Light traveling in the forward direction becomes polarized vertically by the input polarizer. The polarization dependent isolator, or Faraday isolator, is made of three parts, an input polarizer (polarized vertically), a Faraday rotator, and an output polarizer, called an analyzer (polarized at 45°). It is made of three parts, an input polarizer, a Faraday rotator and an analyzer. It has been shown that a crucial requirement for any kind of optical isolator (not only the Faraday isolator) is some kind of non- reciprocal optics Polarization dependent isolator Figure 2: Faraday isolator allows the transmission of light in only one direction. Specifically for an optical isolator, the values are chosen to give a rotation of 45°. Where, ν \nu is the Verdet constant of the material (amorphous or crystalline solid, or liquid, or crystalline liquid, or vaprous, or gaseous) of which the rotator is made, and d d is the length of the rotator.
The angle of rotation, β \beta, is given by, The magnetic field, B B, applied to the Faraday rotator causes a rotation in the polarization of the light due to the Faraday effect. The main component of the optical isolator is the Faraday rotator.
Main article: Faraday effect Figure 1: The optical circuit symbol for an isolator Faraday effect
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