A CW lightwave modulated by a continuously reiterated autocorrelated spectrum-spreading signal is launched into an end of a span of ordinary optical fiber cable. Portions of this lightwave back propagate to the launch end from a continuum of span locations because of innate fiber properties including...http://www.google.de/patents/US7268863?utm_source=gb-gplus-sharePatent US7268863 - Natural fiber span reflectometer providing a spread spectrum virtual sensing array capability
