ENHANCEMENT OF THE PRECISION OF FIBEROPTIC INTERFEROMETERS BY USING COUPLERS WITH HIGH SPECTRAL POWER OR ANTISYMMETRIC SUPERMODE CUTOFF

It is shown that in 2x2 single-mode optical-fiber directional couplers operating with cutoff of the antisymmetric normal mode of a composite waveguide, the additional stray phase shift of the waves in the forwa rd and cross channels (found in normal couplers) vanishes. Thus, by us ing these couplers (instead of the usual ones) in various interferomet ers, the precision can be enhanced substantially. It has also been sho wn that the precision of interferometers with wide-band radiation sour ces (such as white-light interferometers and fiber-optic gyroscopes) c an be improved by replacing the usual couplers with couplers of high s pectral power whose splitting ratio can execute a large number of osci llations within the radiation line width, efficiently eliminating the afore-mentioned stray phase shift. (C) 1997 American Institute of Phys ics. [S1063-7850(97)03207-2]