  The achromatic phase shifter (APS) is a component of the Bracewell nulling
interferometer studied in preparation for future space missions (viz.
Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets.
Several possible designs of such an optical subsystem exist. Four approaches
were selected for further study. Thales Alenia Space developed a dielectric
prism APS. A focus crossing APS prototype was developed by the OCA, Nice,
France. A field reversal APS prototype was prepared by the MPIA in Heidelberg,
Germany. Centre Spatial de Li\`ege develops a concept based on Fresnel's
rhombs. This paper presents a progress report on the current work aiming at
evaluating these prototypes on the SYNAPSE test bench at the Institut
d'Astrophysique Spatiale in Orsay, France.
