Patent ID: 7561768

Claim:
An optical branching device comprising: a first lens member comprising a transmitting plane surface as an incidence plane and a transmitting convex surface as an output plane, the transmitting convex surface having an approximate center of curvature in the transmitting plane surface and having a wavelength-selective mirror surface which transmits light of a first wavelength and reflects light of a second wavelength; and a first optical fiber and a second optical fiber firmly affixed on the transmitting plane surface of the first lens member, wherein the approximate center of curvature of the transmitting convex surface is an intersection point of the transmitting plane surface and an optical axis of the first lens member, wherein positions for affixing the first optical fiber and the second optical fiber on the transmitting plane surface are approximately symmetric with respect to the optical axis of the first lens member, whereby the light of the second wavelength, which is one of the wavelengths of light emitted from the first optical fiber and is reflected and converged by the wavelength-selective mirror surface, enters into the second optical fiber.