Optical multiplexing/demultiplexing method, optical multiplexing/demultiplexing circuit, and manufacturing method thereof

An optical multiplexing and demultiplexing circuit, wherein

• a polished surface of a coated optical fiber whose side surface is polished to a core or a vicinity of the core and a polished surface of an optical waveguide whose propagation constant varies in a longitudinal direction and whose side surface is polished to a core or a vicinity of the core are joined.

A manufacturing method for an optical multiplexing and demultiplexing circuit, the method comprising:

• arranging, face to face, a polished surface of a coated optical fiber whose side surface is polished to a core or a vicinity of the core and a polished surface of an optical waveguide whose propagation constant that varies in a longitudinal direction and whose side surface is polished to a core or a vicinity of the core;
• and
• fixing the polished surface of the coated optical fiber and the polished surface of the optical waveguide so that a desired branching ratio is obtained from one end of the coated optical fiber to the end, distal to the former end, of the optical waveguide by relatively moving the polished surface of the coated optical fiber and the polished surface of the optical waveguide.