an improved process for extruding plastic optical fiber without the need to prepare a preform is provided . specifically , it was discovered that conventional extrusion techniques , e . g ., screw extruders , tended to introduce an undesirable amount of particulate contaminants which increased the loss of the drawn fiber . to overcome this problem , the invention substantially reduces the number of mechanical interactions that contribute to such contamination . the process of the invention does so by using fluid pressure , instead of , e . g ., screw extruders , to induce polymer flow . the process also controls the flow characteristics of the polymer , or halts the flow altogether , without mechanical controls . specifically , the temperature of the sections through which the polymer flows is controllably adjusted , such that it is possible to bring the polymer to a desired flow rate or even to a solid state to provide a plug .