Single-mode fibers and fiber control unit: schematic shows the various fiber subsections and functions. The entrance of the fibers are anti-reflection coated. The optical path length is adjusted by piezo-driven fiber coils. The direction of linear polarization is aligned by motorized fiber twisters. The fibers of these subsections are connected through optimized E2000 connectors. The integrated optics beam combiner − operated at 200 K − is connected through a dedicated V-groove assembly.