Cored wire, method and device for the production of the same

A consumable cored wire for measuring a temperature of a molten steel bath, the cored wire comprising:

• an optical fiber;
• a metal pipe laterally surrounding the optical fiber and configured to melt upon exposure to the molten steel bath;
• and
• an intermediate layer arranged between the metal pipe and the optical fiber,
• wherein the intermediate layer comprises a plurality of fibers formed into a rope which fully encircles the optical fiber,
• wherein the intermediate layer is formed of a fused material and is configured such that pieces of the intermediate layer are fluidized upon exposure to the molten steel bath and form a molten globular layer,
• wherein the pre-melted density of the intermediate layer is 0.3 to 1.7 g/cm3, and
• wherein an interface between the molten globular layer and a remaining unbelted portion of the intermediate layer is gas porous and permits the passage of combustion products of the intermediate layer in a direction opposite the fused intermediate layer material.