Method for polarization compensation and free-space optical communication system for aircraft

A communication system comprising:

• a receiver device configured to receive a first electromagnetic wave and a second electromagnetic wave having amplitude and frequency different than the amplitude and the frequency of the first electromagnetic wave, wherein the first electromagnetic wave and the second electromagnetic wave pass through a physical medium before reaching the receiver device;
• an analysis module, configured to determine a polarization of the first electromagnetic wave received by the receiver device;
• and
• a polarization compensation module configured to compensate for polarization distortion caused by the physical medium to the received first electromagnetic wave, wherein the polarization compensation module includes a system of at least three electromagnetic retarders,
• wherein the at least three electromagnetic retarders include an achromatic retarder or a super achromatic retarder,
• wherein the polarization distortion is determined by the communication system using the polarization of the first electromagnetic wave, and
• wherein the polarization compensation module is configured to set the at least three electromagnetic retarders to compensate for the polarization distortion.

A method for polarization compensation comprising:

• generating a first electromagnetic wave and a second electromagnetic wave having amplitude and frequency different than the amplitude and the frequency of the first electromagnetic wave;
• passing the first electromagnetic wave and the second electromagnetic wave through a physical medium;
• receiving the first electromagnetic wave and the second electromagnetic wave after the first electromagnetic wave and the second electromagnetic wave pass through the physical medium;
• sending the received first electromagnetic wave through at least one electromagnetic retarder of a system of electromagnetic retarders after the receiving and the passing of the first electromagnetic wave through the physical medium, wherein the system of electromagnetic retarders includes an achromatic retarder or a super achromatic retarder,
• measuring an intensity of the first electromagnetic wave after the first electromagnetic wave passes through the at least one of the electromagnetic retarders in the system of electromagnetic retarders;
• determining a polarization of the first electromagnetic wave after the first electromagnetic wave passes through the at least one of the electromagnetic retarders;
• calculating positions of the electromagnetic retarders in the system of electromagnetic retarders based on the determined polarization of the first electromagnetic wave and on a polarization of the first electromagnetic wave before the sending step, wherein the calculated positions of the electromagnetic retarders are determined to compensate for distortion of the first electromagnetic wave by the physical medium;
• and
• adjusting the electromagnetic retarders in the system of electromagnetic retarders to conform to the calculated positions, and
• compensating a polarization of the second electromagnetic wave by passing the second electromagnetic wave through the electromagnetic retarders after the adjusting of the electromagnetic retarders.