| 摘要 |
PURPOSE:To obtain the optical branching filter with which optical fibers are easy to install and which is capable of branching the rays of a small wavelength difference by using refractive index distribution type lenses as lenses. CONSTITUTION:The rays of wavelengths lambda1, lambda2 emitted from an optical fiber 2 are made to parallel rays by a refractive index distribution type lens 7 of 1/4 pitch and enter a reflection type diffraction grating 1. After the rays are diffracted by the diffraction angle corresponding to the wavelengths lambda1, lambda2 and are entered to a refractive index distribution type lens 8 of 1/4 pitch, they are condensed at its exit end face and the rays of, e.g., wavelengths lambda1, lambda2 are entered to refractive index distribution type lenses 9, 10 of 1/2 pitch respectively. Next, the ray of the wavelength lambda1 is condensed at the position of the exit side end face assuming point symmetry with the incident position at the incident side end face with respect to the center of the lens 9 by said lens and is propagated to an optical fiber 3. At the same time, the ray of the wavelength lambda2 is condensed by the lens 10 and is propagated to the optical fiber 4. |
