Method and apparatus for drawing optical fibers

A method of drawing an optical fiber from a preform having a cylindrical cross section, comprising the steps of:

• reflecting a laser beam from a first oscillating mirror onto a second oscillating mirror mounted in orthogonal relationship to the first mirror;
• oscillating the mirrors at the same amplitude and frequency but 90.degree. out of phase to form a patterned laser beam having an annular cross section;
• reflecting the annular beam, from a frustoconical reflector, onto the periphery of a portion of the preform which is axially positioned therein, to form a melt zone in the preform of length L.sub.1 ;
• modulating the amplitude of the oscillating mirrors to reciprocate the annular beam axially of the preform to extend the melt zone to a length L.sub.2, where L.sub.2 >L.sub.1 ;
• and
• drawing the optical fiber from the extended melt zone.

Apparatus for drawing a fiber from a preform, comprising:

• first and second reflecting means, capable of oscillatory motion, for reflecting a beam of high energy radiation;
• means for oscillating the mirrors to cause a predetermined beam pattern to be formed;
• means for directing said patterned beam onto said preform to form a melt zone;
• and
• means for drawing the fiber from the melt zone.

An apparatus for drawing an optical fiber from a preform having a cylindrical cross section, comprising:

• a first mirror capable of oscillatory motion;
• a second mirror capable of oscillatory motion that is 90.degree. out of phase with the motion of the first mirror and is mounted in orthogonal relation to the first mirror;
• a laser to generate a beam which is reflected from the first mirror to the second mirror to form a patterned beam having an annular cross section reflected from the second mirror;
• a frustoconical reflector to reflect the annular beam toward the preform, fed axially therein, to form a melt zone in a portion of the preform;
• a modulation apparatus to modulate the oscillatory motion of the mirrors to vary the diameter of the annular pattern to expand the size of melt zone;
• and
• a drawing apparatus to draw the optical fiber from the melt zone.