| 摘要 |
PURPOSE:To improve the coupling efficiency to optical transmission line by using an optical fiber which is smaller in radius of core, is larger in opening and is provided with a short focus lens. CONSTITUTION:An optical fiber 7 which is smaller in the radius R of its core 6 than the radius R of a core 4, is larger in numerical aperture than an optical fiber 3 and is provided with a short focus lens 8 such as of spherical lens or the like is disposed between a semiconductor laser 1 and the optical fiber 3. Then, the output light directed from the optical fiber 7 to the short focus lens 8 becomes the one which can be regarded as the light from a minute light source and the output light of the short focus lens 8 for the optical fiber 3 equivalently has the radis R of about the same as that of the core 4, thus approximately forming parallel rays. Hence, the efficiency of the optical coupling between the short focus lens 8 and the optical fiber 3 increases and since the peripheral part of the output light of the short focus lens 8 is of gaussian type and of weak light intensity, the coupling efficiency from the semiconductor laser 1 up to the optical fiber 3 increases. |
