Fig. 2From: Realization of a polarization-insensitive optical frequency-domain reflectometer using an I/Q homodyne detectionSchematic representation of different 90 degree optical hybrid implementations. a free space implementation consisting of half-wave plates (λ/2), quarter-wave plates (λ/4), polarizing beam splitters (PBS), beam combiners and mirrors. b fiber optical implementation using phase shifters (PS) and combinersBack to article page