Method for manufacturing a preform and preform for drawing a microstructured optical fiber

A method for manufacturing a preform for drawing a microstructured optical fiber, comprising the steps of:

• arranging a core element and multiple sub-elements to form a bundle, wherein the bundle has a longitudinal axis in collinear relationship with the preform, and wherein the core element has a cylindrical shape;
• twisting the multiple sub-elements by a specified angle about the longitudinal axis, wherein a pattern defined by a cross section of the sub-elements and by a cross section of the core element remains preserved along a length of the perform, and wherein the core element is not twisted;
• inserting the bundle into a casing;
• and
• fusing the casing and the bundle at least partially together by heating the casing, the core element and the sub elements above a transformation point of a respective material of which the casing, the core element and the sub-elements are made, so as to at least partially eliminate empty cavities between the sub-elements, between the sub-elements and the core element, and between the sub-elements and the casing.

A preform for drawing a microstructured optical fiber in a drawing apparatus, in which one end of the preform is heated and the optical fiber is drawn from said one end, comprising:

• a core area defining a longitudinal axis in collinear relationship with the preform;
• multiple substructure elements extending along the longitudinal axis and being helically arranged around the longitudinal axis;
• and
• a casing in surrounding relationship with said substructure elements, wherein a pattern defined by a cross section of the substructure elements varies along a length of the preform only as a function of a helical twist of the preform, and wherein the core element, the substructure elements and the casing are at least partially fused together.