An optical waveguide fiber having an effective area of greater than about 60 m2 at a wavelength of about 1550 nm, a dispersion slope of less than 0. The control system includes an observer configured to estimate friction torque occurring in the vicinity of the motor shaft on the basis of the rotation position and an application voltage to the motor. The vinyl alcohol polymer composition is suitably usable as a coating agent having good storage stability and little uneven applicability, and as gas-barrier material, in particular laminate having excellent gas-barrier properties under high-humidity conditions. The strip heating element is contiguous with the bottom surface and is attached thereto by a gasket extending around the peripheral edge of the strip heating element.