Evaluation of bending-induced birefringence based on stimulated four-photon mixing

In a single-mode fiber, the birefringence introduced by lateral internal stress caused by bending is evaluated from the measurement of the frequency shift of anti-Stokes light generated by stimulated four-photon mixing. The birefringence as a function of bending curvature is measured at a pump wavelength of 1.06 microm. Bending-induced birefringence of 7 x 10(-5), which corresponds to a frequency shift of 1060 cm(-), is found to be introduced by a bending curvature of 2.8 mm. Experimental results are in good agreement with theoretical predictions.