PURPOSE: To prevent cross-talk by cutting off leakage light incident to the end surface of a cladding layer, by providing a light-shielding film, covering the end surface of the cladding layer, between the counter terminal surfaces of a multicore optical fiber.

CONSTITUTION: In the end surface of a multicore optical fiber 22, a light-shielding film 34 is formed on the end surface of a cladding layer 25. Such a fiber 22 is used for an optical connection with the other multicore optical fibers 21 by making their connection end surface face to each other. Consequently, part of light transmitted in one fiber 21, even if emitted to an end surface part other than core parts 24aW24c of the other counter fiber 22 at the connection part, is shielded from by the light- shielding film 34. Thus, the leakage light is intercepted by the light-shielding film 34, so the generation of cross-talk is prevented.