1. An optical multiconductor of the silica glass type characterized in that the multiconductor comprises 10.sup.2 to 10.sup.7 optical fibers of the silica glass type fused to one another, each of the optical fibers comprising a core made of doped silica glass and occupying at least 20% of the fiber in cross sectional area, and a cladding layer made of a material selected from the group consisting of doped silica glass and undoped silica glass, said cladding layer being formed on the core, said core having a refractive index distribution satisfying the following expression: EQU n2.gtoreq.n1+0.50(n0-n1) wherein n0 is the refractive index of the core at its center, n1 is the refractive index of the core at its outermost portion, and n2 is the refractive index of the core at a position centered about the axis of the core and having an average radius of 0.65r1, r1 being the average radius of the core.