Enhancement of the precision of fiber-optic interferometers by using couplers with high spectral power or antisymmetric supermode cutoff

Abstract

It is shown that in 2×2 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 forward and cross channels (found in normal couplers) vanishes. Thus, by using these couplers (instead of the usual ones) in various interferometers, the precision can be enhanced substantially. It has also been shown that the precision of interferometers with wide-band radiation sources (such as white-light interferometers and fiber-optic gyroscopes) can be improved by replacing the usual couplers with couplers of high spectral power whose splitting ratio can execute a large number of oscillations within the radiation line width, efficiently eliminating the afore-mentioned stray phase shift.