Abstract: An optical communications terminal including a polarizing element responsive to a first linearly polarized optical beam and rotating the first linearly polarized optical beam in a first linear direction, a beam separator responsive to and passing the first linearly polarized optical beam, and a circular polarizing element responsive to the first linearly polarized optical beam from the beam separator and circularly polarizing the first linearly polarized optical beam for transmission, where the circular polarizing element is switchable between two orthogonal switching states. The terminal receives a circularly polarized optical beam from another terminal and linearly polarizes the circularly polarized optical beam from the other terminal in a second linear direction that is orthogonal to the first linear direction and the beam separator directs the circularly polarized optical beam from the other terminal in a direction away from the polarizing element.

Abstract: An optical communications terminal including a polarizing element responsive to a first linearly polarized optical beam and rotating the first linearly polarized optical beam in a first linear direction, a beam separator responsive to and passing the first linearly polarized optical beam, and a circular polarizing element responsive to the first linearly polarized optical beam from the beam separator and circularly polarizing the first linearly polarized optical beam for transmission, where the circular polarizing element is switchable between two orthogonal switching states. The terminal receives a circularly polarized optical beam from another terminal and linearly polarizes the circularly polarized optical beam from the other terminal in a second linear direction that is orthogonal to the first linear direction and the beam separator directs the circularly polarized optical beam from the other terminal in a direction away from the polarizing element.

Abstract: An optical communications system including two communications terminals in communication with each other using optical signals having the same wavelength. Both terminals include a half-wave plate polarizer for rotating linearly polarized optical signals and a quarter-wave plate polarizer for circularly polarizing the optical signals. The quarter-wave plate polarizers are oriented 90° relative to each other so that circularly polarized optical signals sent from one terminal to the other terminal are linearly polarized 90° relative to a transmission polarization orientation to be separable from the transmitted optical signals by a beam splitter.

Abstract: An optical communications system including two communications terminals in communication with each other using optical signals having the same wavelength. Both terminals include a half-wave plate polarizer for rotating linearly polarized optical signals and a quarter-wave plate polarizer for circularly polarizing the optical signals. The quarter-wave plate polarizers are oriented 90° relative to each other so that circularly polarized optical signals sent from one terminal to the other terminal are linearly polarized 90° relative to a transmission polarization orientation to be separable from the transmitted optical signals by a beam splitter.

Abstract: A holographic optical element (HOE) includes a substrate structure having rotational symmetry with respect to a rotational axis for rotatively supporting at least two holograms. A first hologram on the substrate structure in the path of a normally incident beam diffracts the beam by a first acute angle and in a first radial direction from the rotational axis to a first redirected path. A second hologram on the substrate structure in the first redirected path diffracts the beam by a different second acute angle and in an opposite second radial direction from the rotational axis to a second redirected path. As a result, the two holograms may be used to achieve a second redirected path at an angle to the rotational axis that has a size which is the difference between the size of the first angle and the size of the second angle.