An optical fiber device may include a core including a primary section and a secondary section. The secondary section may include at least one insert element inserted within the primary section at an off-center location with respect to a center of the primary section. The secondary section may twist about an axis of the optical fiber device along a length of the optical fiber device. A rate of twist at which the secondary section twists about the axis may increase from a first end of the optical fiber device toward a second end of the optical fiber device. The secondary section being twisted about the axis may cause an optical beam, launched at the first end of the optical fiber device, to be at least partially converted to a rotary optical beam at the second end of the optical fiber device.