A disconnect device comprises a tubular member having a window for receiving an engagement member, and a sleeve having connected and disconnected positions. The coupling bar includes an electrically insulating support with two parallel grooves and metallic strips engaged in the grooves. By the invented safety procedure the optical input power fed into said optical fiber system is automatically shut off or at least reduced in case of an unintended escape of light from at least one fiber. The nanostructure can include, but is not limited to, SnO2 nanowires, SnO2 nanoribbons, and SnO2 nanotubes.