DIELECTRIC MIRROR EMBEDDED OPTICAL-FIBER COUPLERS

Dielectric mirrors in multimode and single-mode silica fibers have bee n produced by a fusion-splicing technique. Mirrors oriented normally a nd at a 45-degrees angle to the axis have been studied. Fibers with an gled internal mirrors serve as compact directional couplers with low e xcess optical loss (almost-equal-to 0.2 dB for multimode and 0.5 dB fo r single mode at 1.3 mum) and excellent mechanical properties. The ref lectance is found to be wavelength dependent and strongly polarization dependent. Far-field scans of the reflected output power measured wit h a white-light source show a pattern that is almost circularly symmet ric. The splitting ratio in a multimode coupler measured with a laser source is much less dependent on input coupling conditions than in con ventional fused biconical-taper couplers. Spectral properties of multi layer mirrors oriented normally to the fiber axis have been investigat ed experimentally, and a matrix analysis has been used to explain the results.