| 摘要 |
PURPOSE:To decrease light losses by formation of a main waveguide and a subwaveguide having a circular shape in section by irradiating the UV light propagated through an optical fiber of graded index type to a photosensitive resin coated on a glass substrate thereby curing the resin. CONSTITUTION:A glass substrate 6 is disposed between an optical fiber 1 and optical fibers 2, 3, and a photosensitive resin is coated thereon. UV light of the wavelength region sensitive to the resin is throttled with a lens and is made incident to the fiber 1. The UV light propagates in the fiber 1, cures the uncured photosensitive resin successively from the end face of the fiber 1 until it arrives at the end face of the fiber 2. The UV light is made incident from the fiber 2 as well to cure the photosensitive resin. The uncured parts are removed by developing, whereby a main waveguide 4 is obtained. In the same manner, the photosensitive resin is coated and the UV light is made incident to the fiber 3. The resin is processed in the same manner, whereby a subwaveguide 5 is obtained. Thus the main waveguide 4 and subwaveguide 5 having a circular shape in section of the diameter approximately equal to that of the fibers are formed. Thus light losses are decreased considerably as compared to conventional branching circuits of a square or trapezoidal shape. |
