For standard single-mode optical-fiber Brillouin scattering light,its frequency shift is a function of temperature or strain. So,the temperature or strain of the optical-fiber can be obtained via detecting Brillouin frequency shift. However,Brillouin scattering distributed optical-fiber sensor (DOFS) has two structures of optical time-domain analyzer and optical time-domain reflectometer. These two DOFS structures have their respective performance and application. It is necessary to select either optical time-domain analyzer or optical time-domain reflectometer for the real application,in order to achieve effective distributed sensing. As for the combination of these two structures in one sensing system by using the same optical devices,the key point is to produce the frequency-shifted reference or probe light. A fiber laser is employed as one optical source,a microwave electro-optical modulator is used to produce the frequency-shifted reference or probe light,and a method named with the orthogonal polarization control is adopted to reduce the effect of the optical-polarization-related problem. A laboratorial system of 25 km distributed optical sensor is realized by combining these two structures,with 3 ℃ in temperature resolution,and 5 m in spatial resolution.