Enclosure and method for sealingly enclosing a space into and/or from which at least one optical fibre is fed to connect to at least one optical component, by providing a flexible protective sheet of substantially moisture resistant material having a pair of sealing strips; and folding and sealing the sheet around the optical component to provide an envelope enclosing the component with the optical fibre(s) sealed between the sealing strips. The invention also concerns an enclosure into and/or from which the optical fibres pass through an aperture, which is sealed by an adherent patch, or flap with the fibres sealed between the exterior surface of the enclosure and an overlying portion of the patch or flap.