Production apparatus for producing an optical fiber cable

A production apparatus for producing an optical fiber cable including an optical fiber having a core and a cladding, and a coating, said production apparatus comprising:

• a drawing furnace for drawing an optical fiber preform and forming said optical fiber having said core and said cladding;
• a reaction furnace, which has introduced in it a hermetic coating forming material gas and said optical fiber drawn from said drawing furnace, wherein said reaction furnace produces a thermal decomposition reaction which precipitates decomposed reaction products of said material gas on the surface of said cladding of said introduced optical fiber, to form an electroconductive hermetic coating;
• an eddy current generation and detection sensor arranged near said hermetic coating to generate and detect an eddy current in said hermetic coating;
• a high frequency power source for generating a high frequency current which is applied to said eddy current generation and detection sensor and is of a frequency sufficiently high for causing said eddy current generation and detection sensor to generate said eddy current in said hermetic coating;
• an average magnetization-intensity changing means for applying said high frequency current from said high frequency power source to said eddy current generation and detection sensor while changing an average magnetization-intensity caused by said high frequency current having a frequency of the current lower than the high frequency of said high frequency current;
• means for calculating an electrical resistance of said hermetic coating from said eddy current detected by said eddy current generation and detection sensor;
• and
• control means for adjusting at least one hermetic coating forming condition and the adjusting by said control means being based on the electrical resistance from said electrical resistance calculating means.