For both modes of crystalfibre, the pattern of holes is generated by stacking hollow glass tubes a millimetre or so in diameter to form a rod several centimetres thick.
One example the company has developed is a crystalfibre that squeezes light into such a narrow core that the intensity of the light modifies the optical properties of the glass itself.
In the second mode of working, the crystalfibre uses the regular array of holes to influence light in much the same way as the arrangement of atoms in a crystal can determine whether electrons are able to travel easily through it and hence whether the crystal is electrically conducting or not.
With a different hole design, crystal fibres can do the opposite trick as well, spreading the light much more evenly across the width of the fibre and thereby reducing non-linear effects.