Length dependence of LP₁₁ mode loss in the quasi-single-mode operating region

The length dependence of LP₁₁ mode loss is obtained experimentally by applying a heterodyne interferometric method. Loss values of the LP₁₁ modes are evaluated for short test fibers 3 to 25 m long in the wavelength region close to the cutoff. The experimental results are coincident with those reported previously. We emphasize that the modal dispersion between the LP₀₁ and LP₁₁ modes is evaluated simultaneously by this method.