Apparatus and method for coating optical fibers

Apparatus for coating an elongated fiber with a coating material in vapor form, comprising:

• (a) a coating chamber through which said fiber moves, said coating chamber including:
• (1) an inner chamber through which said fiber to be coated travels,
• (2) an inlet supplied with said coating material in vapor form;
• (3) flow restriction means in fluid communication between said inlet and said inner chamber for reducing the rate of flow of said coating material traveling from said inlet to said inner chamber, said flow restriction means including:
• (i) circumferential flange means positioned between said inlet and said inner chamber, and surrounding said fiber to be coated, for preventing flow of said coating compound from said inlet to said inner chamber, and
• (ii) small diameter orifice means in said circumferential flange means for providing a reduced rate of flow of said coating compound from said inlet to said inner chamber through said flange means;
• and
• (4) circumferential passage means surrounding said fiber and defining a tortuous reduced dimension path terminating in a circumferential slit, from said flow restriction means to said inner chamber, for supplying said coating material to said fiber,
• wherein said small diameter orifice means and said tortuous reduced dimension path reduce the flow rate and turbulence of said coating compound contacting said fiber;
• and
• (b) means for supplying said coating material in vapor form to said inlet.

A coating chamber for coating an elongated hot fiber with a coating material in vapor form as the fiber moves therethrough, comprising:

• a vertically situated coating chamber including an upper end, a vapor inlet and a cylindrical pipe;
• a circumferential slit inside the coating chamber and displaced from the upper end of the coating chamber by approximately the diameter of said pipe;
• a circumferential flange positioned between the vapor inlet and the slit, for preventing flow of the coating compound from the vapor inlet to the slit;
• at least one narrow opening in the flange between said vapor inlet and said circumferential slit, said at least one narrow opening causing a flow resistance for the coating material in vapor form such that a very uniform flow pattern is achieved, contacting the fiber with substantially identical low vapor speeds from all sides, thereby minimizing intermixing of coating vapors and outside air;
• a tortuous path provided between said flange and said slit;
• and
• a heating jacket for heating the wall of the chamber to a temperature well above the condensation point of the coating material in vapor form and below the decomposition temperature of the coating material in vapor form,
• wherein said at least one narrow opening, said tortuous path and said slit reduce the flow rate and turbulence of said coating compound contacting the fiber.

A coating chamber for coating an elongated hot fiber with a coating material in vapor form as the fiber moves therethrough, comprising:

• a vertically situated coating chamber including an upper end, a vapor inlet, a vapor outlet and a cylindrical pipe;
• p1 a circumferential slit inside the coating chamber and displaced from the lower end of the coating chamber by approximately the diameter of said pipe;
• a circumferential flange positioned between the vapor inlet and the slit, for preventing flow of the coating compound from the vapor inlet to the slit;
• at least one narrow opening in the flange between said vapor inlet and said circumferential slit;
• a tortuous path provided between said flange and said slit;
• and
• wherein exhaust vapors are taken from all sides at the lower end of the coating chamber, thereby avoiding disturbance of the fiber to be coated and minimizing intermixture of coating material in vapor with outside air.