| 摘要 |
PURPOSE:To improve reliability and to reduce connection loss, by using a flat light guide which has such a refractive index distribution that the refractive index is uniform in an optical-axis direction and decreases gradually from a maximum at specific depth from the surface of a transparent substrate outwardly almost to that of the substrate at a distant position in a cross section perpendicular to the optical axis, and making the width of end surface of the waveguide enough to connect >=2 optical fibers in parallel in the transparent substrate. CONSTITUTION:Light projected from one optical fiber group 4A in a mixing coupler at an angle of incidence less than the numerical aperture NA of the light guide 2 is all confined in the light guide 2, and a beam 5 is reflected inwardly near the boundary between the light guide 2 and substrate 1 and travels zigzag to the other end to enter an output-side optical fiber group 4B. The breadth wise uniformity of the light instensity distribution in the light-guide 2 depends upon the light output power distribution of a grated type optical fiber, the NA of the light guide 2, and the propagation length of the light guide 2, so transmission loss the coupler and output-side fibers is considerably suppressed by selecting the overall length l of the light guide 2 to the suitable length. |
