Optical fiber tapers - a novel approach to single-mode hardware.

We investigate the performance characteristics of single-mode optical fiber tapers. These devices have a standard single- mode fiber geometry at one end and gradually increase in cross section so that the size of the core at the other end is comparable to that of a multimode fiber. These tapers effectively expand the single-mode spot size and are envisioned as basic building blocks in a multitude of optical components. Analytical and experimental studies, at lambda=0.63micron, show that the dominant mode is preserved while traveling through the taper, from either direction. The excess coupling loss between two tapers is less than 0.1db.