Optical fibers and production methods therefor

A method for forming an optical fiber, the method comprising:

• providing a manufacturing intermediate having an elongate body and comprising an outer tube and a plurality of inner tubes, the plurality of inner tubes being arranged in the outer tube, the plurality of inner tubes being arranged in one or more ring structures around, and at least partially defining, an aperture extending through the elongate body along an axial dimension of the elongate body, a boundary of the aperture defining an internal surface of the manufacturing intermediate;
• etching the internal surface of the manufacturing intermediate using an etching substance;
• and
• drawing the manufacturing intermediate along the axial dimension so as to form the optical fiber, the optical fiber being a hollow-core anti-resonant-reflecting fiber comprising a plurality of anti-resonant elements formed from the inner tubes.