Nippon Telegraph and Telephone Corporation

Yuji Fujiwara

Ryoichi Kasahara

Satomi Katayose

Takahiro Kashiwazaki

Junji Sakamoto

Katsuhiko Hirabayashi

To manufacture an optical waveguide including a substrate, a lower cladding layer formed on the substrate, a core layer formed on the lower cladding layer, a sinking prevention layer formed to cover the core layer and the lower cladding layer, and an upper cladding layer formed on the sinking prevention layer, in which the sinking prevention layer is composed of a material having a higher melting point than that of a material composing the lower cladding layer.

Optical waveguide and manufacturing method thereof

An end portion structure of a transmission line of the present invention is a structure in which a protective film with a thickness of 0.5 μm to 3.0 μm is formed on the end surface of the transmission line in place of an end cap formed in an end portion of a transmission line in the related art, and no adhesive is used in a portion through which light passes. The protective film on the end surface works to suppress a bulge of the core. The thickness of the protective film is significantly thinner than the end cap, and thus waveguides facing each other can be brought close to each other. It is possible to reduce the connection loss between two fibers or waveguides facing each other to be 0.5 dB or less. Since no adhesive is used, there is no loss increase caused by adhesive deterioration.

End structure of a waveguide

To provide a planar lightwave circuit capable of being optically connected to a semiconductor optical element or an optical wiring component in a simple, precise, and stable manner without an increase in circuit footprint or the number of fabrication steps or a deterioration of characteristics. By arranging a dummy optical waveguide having a mirror function in the vicinity of an input/output waveguide of an optical functional circuit forming the planar lightwave circuit, a semiconductor optical element or an optical wiring component can be easily aligned with and fixed to the optical functional circuit by monitoring the reflection light intensity from the dummy optical waveguide. When the optical functional circuit has a plurality of input/output waveguides to be optically connected, each input/output waveguide can be identified if the dummy optical waveguides having the mirror function have different reflection properties (such as reflectance, width, position, or reflection wavelength).

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Musashino, Japan

Yuji Fujiwara