METHOD OF PRODUCING PHOTONIC CRYSTAL FIBERS

A method of producing photonic crystal fiber (PCF) preforms, comprising obtaining a plurality of preform capillaries; measuring the wall thickness of each of the plurality of preform capillaries along at least a portion of its circumference at one or more axial positions; selecting a number of preform capillaries from the plurality of preform capillaries at least based on a thickness criterion,; and placing the selected preform capillaries in a glass tube (or jacket tube) to form a PCF preform having at least one ring arrangement of the selected preform capillaries; wherein the selected preform capillaries are oriented such that the portion of each of the selected preform capillaries, within which the measured wall thicknesses vary from the nominal wall thickness by no more than the maximum thickness variation, faces a longitudinal axis of the glass tube, said glass tube being substantially symmetrical about the longitudinal axis.