Optical fiber strain and temperature measurement apparatus

Abstract

By removing remaining components of Rayleigh scattered light, control is sufficiently performed of polarization states even when the wavelength of scattered light has changed. A light source unit configured to generate probe light, a wavelength control unit configured to receive backscattered light emitted from an optical fiber to be tested by the probe light and to output Brillouin backscattered light included in the backscattered light, and a self-delayed heterodyne interferometer to which the Brillouin backscattered light is input are included. The wavelength control unit includes a wavelength separation filter, a variable wavelength filter, an optical intensity measurement unit, and a control unit. The wavelength separation filter has two output ports, outputs and transmits, from one of the two output ports, the Brillouin backscattered light to the variable wavelength filter, and outputs and transmits, from the other output port, Rayleigh scattered light to the optical intensity measurement unit. The optical intensity measurement unit measures a center wavelength and a peak intensity of the Rayleigh scattered light. The control unit controls a cutoff wavelength of the variable wavelength filter in accordance with a direction and amount of change of the center wavelength.