PURPOSE: To provide an optical fiber coupler of which the optical branching ratio is not dependent on wavelengths and a production method featuring excellent mass productivity thereof.
CONSTITUTION: Optical fibers 1 and 2 are arrayed in parallel and, while the parallel arrayed parts are being heated, the front ends and rear ends thereof are held, pulled, fused and stretched to form a coupling part 3. At this time, light of a wavelength of 1.55μm is made incident on the optical fiber 2. The quantity of the light emitted from the optical fiber 1 or the optical fiber 2 is then measured and the optical branching ratio of the coupling part 3 is detected. The fusion and stretching is stopped at the point of the time when the max. rate of the optical branching ratio attains a range of 50±5%, and the production of the optical fiber coupler is completed.
SHIROTA MASAAKI
KAMIYA KAZUO
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