The present invention provides a cassette for coiling at least one optical fiber provided with a splice protection, in which said optical fiber is to be wound in such a manner as to fit closely against an inside peripheral wall of said cassette, said cassette being provided with two entry points in the vicinity of said inside peripheral wall to enable two portions of said optical fiber situated on either side of said splice protection to penetrate into said cassette. According to the invention, said entry points are provided with guide means so that said two portions wind in the same direction, and said splice protection takes up a non-predetermined position in said cassette. The present invention is more particularly adapted to coiling a flat optical fiber ribbon having a splice.