Polarization crosstalk dependence on length in silica-based waveguides measured by using optical low coherence interference

We describe a powerful method for precisely measuring polarization crosstalk dependence on length for birefringent waveguides which uses optical low coherence interference between excited and orthogonally coupled light waves. This method is applied to 10-m long silica-based waveguides with the total polarization crosstalks of 8.9/spl times/10/sup -3/ and 7.5/spl times/10/sup -3/. The spatial resolution is 10 cm and the measurement error for a waveguide part longer than 1 m is /spl les/10%. A comparison of measured and theoretical crosstalk curves for the waveguides enables us to confirm that the bends in the waveguides are the main origin of the crosstalk. The polarization crosstalk per bent section is /spl sim/4/spl times/10/sup -5/.