JPS5635106A - Optical fiber coupler - Google Patents

Abstract

PURPOSE:To make manufacture easy and lower coupling losses by making use of the characteristics that when optical fibers of single mode are elongated in the state that the differences in their refractive indexes are maintained constant to make the core diameter smaller and so the field distributions of light power become conversely larger. CONSTITUTION:An input side optical fiber 41 is elongated in the state that the differences in its refractive indexes are maintained constant, whereby its end face 50 is made small. The core radius thereof is defined as a1. On the other hand, output side optical fibers 42, 43 are elongated in the state that the differences in their refractive indexes are maintained constant, whereby their respective end faces 51, 52 are made small. When the respective core radii are defined as a2, a3, the conditions of a1<a2, a1<a3 are satisfied. The end faces 50 and 51, 52 are opposedly disposed and are fixed by a coupling material 56. Then, the light power field distribution 27 at the end face 50 connotes the light power field distributions 27, 28 of the end faces 51, 52; therefore, the coupling characteristic becomes better. In this way, the manufacture of the coupler is made easy and coupling losses are made lower.