In a bent single-mode fiber, lateral compressive stress under the conditions oflarge deformation induces a birefringence >β. This Permits us to conceive devices which are, for fiber optics, the analogue of fractional wave plates of classical optics. In the meantimewe designed a polarimeter to measure the bending-induced bireflingence and realized aquarter wave plate at λ=1.55 μm with a two-turn optical fiber loop of 26 mm indiameter.