entry plenum 80 is disposed adjacent to the cross flow manifold 70 of the coating deposition chamber 50 the fiber entry plenum comprises an entry orifice 82 and an exit orifice 84 spaced from the entry orifice 82 which communicates with the exhaust outlet portion 78 also the entry plenum 80 includes a purge gas inlet 86 which communicates with a chamber 88 of the fiber entry plenum 80 a fiber exit plenum 60 is disposed adjacent to the reactant gas inlet 54 of the coating deposition chamber 50 the fiber exit plenum 60 comprises an entry orifice 62 an exit orifice 64 spaced from the entry orifice 62 and an exit plenum purge gas inlet 66 which communicates with a chamber 68 of the fiber exit plenum 60 a fiber drawing process is initiated by suspending a perform 14 in the preform feed mechanism 12 and lowering the tip 18 into the furnace 20 such that the preform is heated in the hot zone 22 the fiber 24 is drawn from the tip of the preform and extended first through the fiber entry plenum 80 by threading the fiber 24 through the entry and exit orifices 82 and 84 respectively of the entry plenum 80 then through the cross flow manifold 70 and through the bore 52 of the coating deposition chamber 50 the fiber 24 is then extended through the fiber exit plenum 60 by threading the fiber 24 through the exit plenum entry and exit orifices 62 and 64 respectively from the exit plenum 60 the fiber 24 is then threaded through the polymer coating die 36 the coating concentricity monitor 42 and the.