Patent ID: 8687957

Claim:
A method of using an optical time domain reflectometer (OTDR) means ( 22 ) and a wavelength-dependent reflective (HRD) element in characterizing one or more parameters of a selected optical path of an optical network, said OTDR and said HRD element being connected to said selected optical path at respective first and second mutually-spaced points, said HRD element being highly-reflective at one of two predetermined wavelengths (Î» 1 ,Î» 2 ) and significantly less reflective at the other of the two predetermined wavelengths, neither of the two wavelengths corresponding to a normal operating wavelength of the optical path, the method comprising the steps of: using said optical time domain reflectometer means ( 22 ) connected to said first point of said selected optical path: to launch into the selected optical path at said first point light at each of said two wavelengths (Î» 1 ) and (Î» 2 ), to detect at said first point corresponding backreflected light as a function of time at each of said two wavelengths (Î» 1 ,Î» 2 ) and obtain therefrom first and second OTDR traces (OTDR-Î» 1 ,OTDR-Î» 2 ), respectively, each representing backreflected light as a function of optical distance; to compare the first and second OTDR traces to distinguish a peak corresponding to said HRD element from peaks corresponding to wavelength-independent localized reflectances, and to derive from said peak a value of one or more parameters of either or both of said HRD element and said selected optical path between said first and second mutually-spaced points.