Abstract: The present invention provides a method of storing data in an optical data storage device. The method comprises the step of encoding information and determining a multi-channel grating structure for the encoded information. The method further comprises the step of applying the grating structure to an optical waveguide in a manner such that in use the multi-channel grating will effect a change of a property of optical radiation that passes through the waveguide. The change of the property is characteristic for the encoded information. The present invention further provides an optical read only memory having a multi-channel grating.