According to some embodiments a method of processing an optical fiber comprises the steps of: (i) drawing the fiber at a drawing rate of at least 30 m/sec; and (ii) cooling the drawn fiber in a gas at an average cooling rate less than 5000 C./s, such that said cooling reduces the temperature of the fiber from an entering temperature in the range between 1500 C. and 1700 C. to another temperature in the range between 1200 C. and 1400 C., the gas being at a temperature between 800 C. and 1500 C.; and the thermal conductivity of the gas being not greater than 1.510.sup.4 cal/cm-s-K for at least one temperature within a range of 800 C. to 1500 C. at one atm (atmosphere) pressure absolute.

An optical fiber draw system that prints one or more fiber identifiers on optical fibers is described. In one example, the optical fiber draw system includes a draw furnace, a coating device, a marking device, and a lighting device. The draw furnace generates a glass fiber from a glass preform and the coating device is configured to apply a curable coating composition to the glass fiber. The lighting device applies an ultraviolet or other curing light to form a coating from the curable coating composition. The application and curing of a curable coating composition can be completed one or more times to form one or more coatings on the glass fiber. The marking device applies a tracer marking fluid to a curable coating composition or coating and can be placed at one or more positions along the process pathway.

A method includes heating a hollow-core preform comprising an outer tube and an inner tube. The outer tube includes an inner radius r.sub.ocp and an outer radius R.sub.ocp. The inner tube includes an inner radius r.sub.cp and an outer radius R.sub.cp. The method further includes drawing a hollow-core optical fiber from the hollow-core preform at a draw tension T.sub.g in grams, thereby elongating the outer tube into an outer cladding of the hollow-core optical fiber and the inner tube to a capillary of the hollow-core optical fiber. The draw tension T.sub.g and/or a differential capillary pressure p.sub.c are selected at least in part based on a non-dimensional parameter

[00001]$X_1=\frac{3\left(R_{\mathrm{ocp}}^2-r_{\mathrm{ocp}}^2\right)R_{\mathrm{cp}}\left(p_c{r}_{\mathrm{cp}}-2{}_c\right)}{4{\mathrm{Tr}}_{\mathrm{cp}}\left(R_{\mathrm{cp}}-r_{\mathrm{cp}}\right)},$

where T is the draw tension in dynes and T=981T.sub.g, p.sub.c is in dynes/cm.sup.2, .sub.c in dyne/cm is a surface energy of a glass material forming the inner tube, and 0.5X.sub.10.75.

A method may include: feeding a hollow-core preform into a draw furnace at a preform feed rate V.sub.p; heating the hollow-core preform comprising an outer tube having an inner radius/diameter r.sub.p/ID.sub.preform and an outer radius/diameter R.sub.p/OD.sub.preform; and drawing a hollow-core optical fiber from the hollow-core preform at a fiber draw rate V.sub.f and a draw tension , thereby elongating the outer tube of the hollow-core preform to an outer cladding of the hollow-core optical fiber having an inner radius/diameter r.sub.f/ID.sub.fiber and an outer radius/diameter R.sub.f/OD.sub.fiber; wherein: the interior cavity of the outer tube is under a differential core pressure P.sub.core, the differential core pressure P.sub.core, the inner and outer radii r.sub.p and R.sub.p of the outer tube are selected such that a tight control over target inner and outer radii r.sub.f and R.sub.f and a fiber dimension sensitivity ID.sub.fiber of the outer cladding can be achieved.

The present disclosure relates to a method and an extrusion apparatus (100, 200) to manufacture a soot preform (130). The extrusion apparatus (100 and 200) includes a feed-hopper (104) to feed silica slurry (102) which is pushed within the barrel (106), an iris frame (116) exhibiting a variable diameter to control a diameter of the soot preform (130), drying furnace (118), debinding furnace (122) eliminates moisture and one or more stabilized binders in the soot preform (130) to obtain a glass preform (138) from which an optical fiber (142) is drawn.