An extrusion method and apparatus for producing a cable including at least
one core having at least one transmissive element and at least one pair
of coating layers arranged at a radially outer position with respect to
the core. At least one coating layer of polymeric material and one
coating layer of expanded polymeric material are deposited by
co-extrusion simultaneously and residual pressure not greater than the
external pressure is maintained in a substantially annular interspace
defined between the coating layers. The method avoids the formation of
bubbles at the interface between the at least one coating layer of
polymeric material and the coating layer of expanded polymeric material,
attaining an optimal adhesion between the layers.