PURPOSE: To simplify the adjustment during manufacture and to obtain the titled device contrived to be miniaturized and economized, by a method wherein light emitting elements with the light emitting prts and nonexcited parts disposed in an array along the optical axis are arranged in cascade, so as to couple the light emitting part of the shortest luminous wavelength with an optical fiber.

CONSTITUTION: A groove 10 is formed in the middle of GaAlAs laser diodes in the form of isolating active layers 11 and 11'. If an injected current with an oscillation threshold value of Ith or more is impressed on a terminal 16' but not on a terminal 16, oscillation occurs in the part of current impressing, and the non-excited part of no current impressing serves as an absorption region. Then, synthesizing-branching filter elements 20-1, 20-2 and 20-3 having such a construction with each different luminous wavelength are connected in cascade. In the case of making e.g. 3-wavelength light multiple, the elements 20-1, 20-2 and 20-3 with the light emitting part and the non-excited part disposed in an array on the optical axis of the optical fiber 1 are coupled with the optical axis made uniform with one another in such a manner that luminous wavelengths λ1, λ2 and λ3 are λ1<λ2<λ3. Finally, the optical fiber 1 for transmission is coupled with the element 20-1 of shortest luminous wavelength on the light emission side.