An apparatus for applying at least one cable of one or more optical fibers to a pipe for land or submarine pipelines, said pipe having a longitudinal direction of development, said pipe comprising at least one layer of metallic material and at least one multilayer cladding of said layer of metallic material, the at least one multilayer cladding comprising at least one first cladding layer proximal to said at least one layer of metallic material and at least one second cladding layer distal with respect to said at least one layer of metallic material, opposite to said at least one first cladding layer, the apparatus comprising: - a plurality of supporting modules, each supporting module of said plurality being configured to be operatively associated with a pipe, each supporting module being configured to slide with respect to the pipe along the longitudinal direction of development of the pipe; - a plurality of milling unit, each milling unit being operatively associated with the relative supporting module, each milling unit being configured to make a groove in a peripheral radial portion of said at last one second cladding layer along the direction of development of the pipe, during the relative sliding between the relative supporting module and the pipe, each groove belonging to a plurality of grooves made on said at least a second cladding layer according to a set distribution along different radial directions with respect to the section of the tube along a plane transversal to the longitudinal direction of development of the pipe; - a plurality of laying unit of at least one cable with one or more optical fibers, each laying unit being operatively associated with the relative supporting module, each laying unit being configured to lay said at least one cable with one or more optical fibers within the relative groove, during the relative sliding between the supporting module and the pipe along the longitudinal direction of development of the pipe; - a plurality of extruding unit, each extruding unit being operatively associated with the relative supporting module, each extruding unit being configured to release a filling material of the relative groove and to embed said at least one cable with one or more optical fibers within said groove, during the relative sliding between the relative supporting module and the pipe along the longitudinal direction of development of the pipe, melting the filling material of the groove with the radially peripheral portion of said at least one second cladding layer in which the groove is made. - a plurality of supporting modules, each supporting module of said plurality being configured to be operatively associated with a pipe, each supporting module being configured to slide with respect to the pipe along the longitudinal direction of development of the pipe; - a plurality of milling unit, each milling unit being operatively associated with the relative supporting module, each milling unit being configured to make a groove in a peripheral radial portion of said at last one second cladding layer along the direction of development of the pipe, during the relative sliding between the relative supporting module and the pipe, each groove belonging to a plurality of grooves made on said at least a second cladding layer according to a set distribution along different radial directions with respect to the section of the tube along a plane transversal to the longitudinal direction of development of the pipe; - a plurality of laying unit of at least one cable with one or more optical fibers, each laying unit being operatively associated with the relative supporting module, each laying unit being configured to lay said at least one cable with one or more optical fibers within the relative groove, during the relative sliding between the supporting module and the pipe along the longitudinal direction of development of the pipe; - a plurality of extruding unit, each extruding unit being operatively associated with the relative supporting module, each extruding unit being configured to release a filling material of the relative groove and to embed said at least one cable with one or more optical fibers within said groove, during the relative sliding between the relative supporting module and the pipe along the longitudinal direction of development of the pipe, melting the filling material of the groove with the radially peripheral portion of said at least one second cladding layer in which the groove is made.