Patent ID: 8218933

Claim:
A method of producing a substantially planar substrate having waveguide channels, which method comprises: (i) providing a tube of a substrate material; (ii) depositing silica layers on the inside of a tube, the silica layers being doped with a photosensitive material; (iii) drawing the tube so that the cross-sectional size of the tube is reduced; (iv) before or after the reducing of the cross-sectional size of the tube, causing the tube to collapse into a flat shape by applying a low pressure to the tube, whereby the deposited silica layers together form a photosensitive silica layer; (v) cutting to required lengths the tube which has been collapsed and reduced in cross-sectional size; and (vi) using laser writing to define waveguide channels in the cut lengths of the tube and thereby to produce the planar substrate having the waveguide channels.