A novel torsion sensor based on a long-period fiber grating (LPFG) written by high-frequency CO 2 laser pulses is demonstrated. The resonant wavelength shifts linearly toward longer wavelength as the LPFG is twisted clockwise, whereas it shifts toward linearly shorter wavelength as the LPFG is twisted anticlockwise. Such a torsion sensor can, not only measure the applied twist rate directly, but also determine the twist direction. Accordingly, this all-fiber absolute torsion sensor could find important engineering applications in the field of smart structures where the ability for the sensor to be embedded into the structure is critical.