Abstract: The invention provides a method of forming a grating structure on a photosensitive waveguide, involving: moving the waveguide relative to a light source in the longitudinal direction of the grating, directing coherent light from the light source perpendicularly to the direction of relative movement of the waveguide and irradiating spaced-apart regions of the waveguide to form the grating structure, modulating the light and, as a separate step, passing the light through a shutter in its passage between the light source and the waveguide, and controlling the shutter to effect shuttering of the light in synchronisation with the relative movement of the waveguide during formation of the grating structure, in order to control the irradiation of said waveguide so as to keep constant the refractive index in the waveguide core averaged over a full period of said grating structure.

Abstract: A method of accurately setting the center wavelength of a fiber grating fixed in a temperature compensation package, the method comprising the steps of: fixing the grating to the package and altering the size of the package in a post processing step. The altering step can comprise elongating or compressing the package so as to substantially permanently alter the size of the package.