Patent ID: 6888992

Claim:
A method of making a photonic crystal fibre, comprising: (i) providing a plurality of elongate canes, each having a longitudinal axis, a first end and a second end, at least some of the canes being capillaries each having a hole parallel to the longitudinal axis of the cane and running from the first end of the cane to the second end of the cane; (ii) forming a preform by forming the canes into a stack and fusing them together, the canes being arranged with their longitudinal axes substantially parallel to each other and to the longitudinal axis of the stack; (iii) drawing the preform into the fibre whilst maintaining the hole of at least one capillary in communication with a source of fluid at a first pressure whilst maintaining the pressure around the said hole at a second pressure, wherein the hole at the first pressure becomes, during the drawing process, a size different from that which it would have become without the pressure difference.