Helically twisted photonic crystal fibres

Photonic crystal fibres (PCF) are strands of glass, not much thicker than a human hair, with a lattice of hollow channels running along the fibre. If they are continuously twisted in their production, they resemble a multi-helix. Twisted PCFs show some amazing features, from circular birefringence to conservation of the angular momentum. The biggest surprise, however, is the robust light guidance itself, with no visible fibre core. The basis for this are forces which, like gravitation, are based on the curvature of space.