Polarization State Preparation Assembly

The polarization state preparation assembly separates light by its left- or right-handed circularly polarized states. It first splits the incoming light from the telescope assembly into the Payload beacon and transmission lasers based on their wavelengths. This split is accomplished by using a dichroic, which diverts the beacon laser into the tracking assembly while passing the transmission laser into the polarization state preparation assembly. The received circularly-polarized transmission laser is passed through a quarter-wave plate, converting it into linearly polarized light. This light is then split by a polarizing beam splitter (PBS) into two separate paths, corresponding to data sent with left- or right-handed circular polarization. These two beams are then collimated into fibers coupled to high-bandwidth avalanche photodiodes (APDs) in the signal decoding assembly.