<title>Abstract</title>
We propose a novel one-dimensional radiation distribution sensing method using an optical fiber sensor based on wavelength spectrum unfolding for the application in the measurement of the high dose rate hot spots inside the Fukushima Daiichi Nuclear Power Station (FDNPS) buildings. The proposed method estimates the incident position of radiation to the fiber by the unfolding of wavelength spectrum output from the fiber edge on the premise that the attenuation length of light along the fiber depends on a wavelength. Because this method measures integrated light intensity, it can avoid the problem of counting loss and signal pile-up, which occurs in a radiation detector with the pulse counting mode under the high dose rate field. Basic properties of source position detection were confirmed through basic experiments using an ultraviolet light source and 90Sr/90Y radioactive point source.