Abstract

In this paper, a single-mode fiber directional coupler with strong coupling made by the polished technique is studied. Such a coupler consists of two parallelly spliced fibers with their cores touched each other. The modes become coupled directly without any evanescent fields, so the coupled mode theory fails to expound. Since the core of the coupling zone of the coupler plays most important role in guidance of lightwave, it cannot be neglected like a fused single-mode coupler with large taper ratio and/or small 7-value^/1/.

© 1986 Optical Society of America