Cables; electrical conductors; electrical connectors; cables and conductors for telecommunication; optical fibres; optical fibre cables; telecommunication lines and systems; optical-fibre telecommunication lines and systems; wavelength multiplexing telecommunications lines and systems; systems and lines of distribution of interactive services; opto-electronic systems; passive optical-fibre systems and lines; optical apparatus and instruments; devices for generating, switching, combining, amplifying, reprocessing, transmitting and receiving optical signals; cable-television devices; plannar optical devices; lasers; optical amplifiers; optical modulators; cables, electrical conductors, optical fibres and telecommunications lines and systems having water swellable powders for water blocking properties