| 摘要 |
PURPOSE:To greatly shield the light of the mode propagating through harmful clad layer emitted to the optical fiber end part in a simple method, by furnishing the end part of optical fiber with a mask to shield the clad layer and resin coated layer end plane other than the core part. CONSTITUTION:When a luminous flux from a light source 2 is converged by a lens 3 and caused to enter, the luminous flux is transmitted in plural modes when propagating through an optical fiber 1. In order to prevent the light of this harmful mode from entering a photo detector 5, a mask 6 is fitted to the exit end of the optical fiber 1. The mask 6 is in the form of a cup of which inside diameter 61 matches with the outside diameter of a coated layer 13 of the optical fiber 1, and has a hole 62 roughly equal to the diameter of the core 11 of the optical fiber provided in the central part of the bottom thereof. Of the light consisting of plural modes propagating through the optical fiber 1, the light of the modes propagating through the core 11 is emitted through the hole 62, and reaches the photo detector 5 by way of the lens 4. The light of the mode propagating through the clad 12 is shielded because the bottom of the mask 6 covers the end plane of the clad 12. |
