An optical module comprising a column-shaped mounting member having a through hole extending along the central axis thereof and having a mounting surface formed by incising a part of the mounting member so as to expose the interior surface of the through hole; and an optical fiber inserted in the through hole and secured in a configuration such that the optical fiber protrudes with a specified length onto the mounting surface. The structure, in which a Bragg diffraction grating is formed in such protruding part of the optical fiber on said mounting surface, can prevent the occurrence of a change in reflective characteristic of the Bragg diffraction grating.