Abstract: A method of forming a complete grating structure on a photosensitive waveguide is disclosed comprising the steps of: (a) writing an initial portion of the grating structure on the waveguide; (b) testing the properties of the initial portion to determine a series of parameters of the initial portion; (c) utilizing the parameters to alter the characteristics of a subsequently written portion of the grating structure to provide for an improved form of grating structure; (d) iterating the steps (a) to (c) so as to form the complete grating structure. The writing can be performed utilizing a coherence pattern formed from the interference of two coherent beams on the waveguide. The characteristics can include the intensity or phase of the subsequently written portion. The testing may include determining the spectral reflectance response of the initial portion or determining the spectral phase delay of the initial portion.