Patent ID: 7336866

Claim:
An optical fiber device including: two optical fibers the tips of which are arranged facing each other and are optically coupled, rod lenses provided one each at each tip portion of said two optical fibers, and an optical functional element interposed between each front face of said two rod lenses; wherein said two rod lenses have the same refractive index distribution; each front face of said two rod lenses is respectively formed, at the approximate midpoint of a position where the mode field diameter of the propagating light emitted from said optical fiber at which the same rod lens is provided and propagating through the interior of the rod lens forms a local maximum, and a position where the mode field diameter, in case the same rod lens is assumed to be extended in the axial direction, forms a local minimum subsequent to said local maximum, in the propagation direction of the same propagating light, perpendicularly to said axis; and both front faces of said two rod lenses are arranged symmetrically with respect to a point at which the transmitted light, emitted from one front face to the exterior, forms a beam waist.