Arrangement for time-resolved optical backscatter measurement at optical waveguides

Claim 1

An apparatus for time-resolved optical backscatter measurement (OTDR=Optical Time Domain Reflectometry) at optical waveguides, in particular for space-resolved temperature measurement, comprising: a light source, which emits light of a specified wavelength; an optical waveguide; first means for coupling the light from the light source into the optical waveguide; second means for coupling backscattered light, which includes components originating from a Rayleigh scattering and a Raman scattering, out of the optical waveguide; third means for measuring the backscattered Raman component coupled out of the optical waveguide; and a filter device disposed between the second and third means, said filter device selectively attenuating the backscattered light component originating from the Rayleigh scattering; wherein the filter device comprises a polarizing beam splitter, behind which a quarter-wave plate and an interference filter are disposed in succession in the transmission direction, both of which are tuned to the wavelength of the light emitted by the light source, and wherein at an output of the filter device radiation which is reflected by the interference filter and is reflected out to the side by the polarizing beam splitter is taken off; wherein the first and second means comprise a common polarizing beam splitter, which is disposed between the light source and the optical waveguide in the transmission direction, and a first optical focusing system disposed between the common polarizing beam splitter and the optical waveguide; the common polarizing beam splitter of the first and second means and the polarizing beam splitter of the filter device combined into a single polarizing beam splitter; a deflecting prism disposed at said single polarizing beam splitter, on the side of the emerging backscattered light, said deflecting prism deflecting the backscattered light emerging from said single beam splitter back into the beam splitter; and the quarter-wave plate and the interference filter of the filter device disposed on the side of said single polarizing beam splitter opposite the deflecting prism.

Claim 2

An apparatus for time-resolved optical backscatter measurement (OTDR=Optical Time Domain Reflectometry) at optical waveguides, in particular for space-resolved temperature measurement, comprising: a light source, which emits light of a specified wavelength; an optical waveguide; first means for coupling the light from the light source into the optical waveguide; second means for coupling backscattered light, which includes components originating from a Rayleigh scattering and a Raman scattering, out of the optical waveguide; third means for measuring the backscattered Raman component coupled out of the optical waveguide; and a filter device disposed between the second and third means, said filter device selectively attenuating the backscattered light component originating from the Rayleigh scattering; wherein the filter device comprises a polarizing beam splitter, behind which a quarter-wave plate and an interference filter are disposed in succession in the transmission direction, both of which are tuned to the wavelength of the light emitted by the light source, and wherein at an output of the filter device radiation which is reflected by the interference filter and is reflected out to the side by the polarizing beam splitter is taken off; wherein the first and second means comprise a common polarizing beam splitter, which is disposed between the light source and the optical waveguide in the transmission direction, and a first optical focusing system disposed between the common polarizing beam splitter and the optical waveguide; the common polarizing beam splitter of the first and second means and the polarizing beam splitter of the filter device combined into a single polarizing beam splitter; a deflecting prism disposed at said single polarizing beam splitter, on the side of the emerging backscattered light, said deflecting prism deflecting the backscattered light emerging from said single beam splitter back into the beam splitter; and the quarter-wave plate and the interference filter of the filter device disposed on the side of said single polarizing beam splitter opposite the deflecting prism.