Metal-doped single-walled carbon nanotubes and production thereof. The guide is associated with a computer controlled surgical navigation system employing an energy-detecting array to track positions of the guide in three dimensional space relative to a known reference point. A returned OTDR signal is received over the first optical transmission path in which status information concerning the first optical transmission path is embodied. The first polarizer film is on the first WV film, wherein diffusive patterns are formed on surface of the first polarizer. The shells enclose a separating element fitted with a multiple number of transversal openings and a multiple number of contact points with the shells, where the transversal openings are offset with respect to the transversal slots so as to create at least four paths deviating the flow of air inside the space encompassed by the two shells.