Method for producing self-forming optical waveguide

A method of manufacturing a self-forming optical waveguide, comprising:

• preparing a photocurable resin and two multicore fibers each having at least n cores (n:
• a natural number of 2 or more), the photocurable resin comprising a core part forming resin that is polymerized when light in a predetermined wavelength band is incident thereon and has a refractive index na after curing, and a cladding part forming resin that is polymerized and cured when light of an intensity equal to or greater than that of the light incident on the core part forming resin is incident thereon and has a refractive index nb after curing satisfying nb<na,
• arranging the two multicore fibers to face each other and arranging the photocurable resin between the multicore fibers,
• making light of an intensity allowing only the core part forming resin to be polymerized incident on the photocurable resin from the cores of the two multicore fibers to cause polymerization and curing of the core part forming resin, thereby forming core parts of optical waveguides within the photocurable resin,
• after the core parts are formed, causing interdiffusion of monomers in the cladding part forming resin around the core parts,
• next making light incident on, and causing propagation thereof in, the core parts, generating light leakage into the cladding part forming resin, that is uncured, around the core parts, and polymerizing and curing the cladding part forming resin around the core parts by the leakage light to form cladding parts, thereby self-forming n optical waveguides in the photocurable resin.