An apodised Bragg grating comprises a base grating section formed by a base order 5 periodic pattern of marks and spaces. The Bragg grating further comprises one or more apodised grating sections that are formed by a periodic pattern of marks and spaces, each defined by the base order pattern from which at least some of the marks are missing. The determination of which marks are missing may be performed by combining the base order pattern with a higher order modulation envelope function.