Patent ID: 7227645

Claim:
Apparatus for measuring polarization mode dispersion (PMD) of an optical waveguide, comprising: (i) broadband light source means ( 10 , 12 ) for applying polarized broadband light to one end of the waveguide ( 14 ), (ii) an interferometer ( 20 ) having an input port ( 18 ) for receiving said light from the waveguide ( 14 ), an output port ( 28 ), means ( 22 ) for dividing the light into first and second components ( 24 A, 24 B), first and second paths for conveying the first and second components, respectively, to said output port ( 28 ) for recombination, and means ( 26 B) for varying the length of one of the first and second paths relative to the other to cause interference between the components upon recombination, (iii) a polarization separator ( 30 ) for receiving the recombined light from the output port and separating said recombined light into first and second interferograms having orthogonal polarization states, (iv) detection means ( 32 X , 32 Y ) for converting the first and second interferograms, respectively, into corresponding first and second electrical interferogram signals (P X (τ),P Y (τ)), and (v) means ( 36 ) for processing the first and second electrical interferogram signals to produce a cross-correlation envelope (E C (τ)) and an auto-correlation envelope (E A (τ)), and determining from the cross-correlation envelope and the auto-correlation envelope the polarization mode dispersion (PMD) of the waveguide.