In the field of the measuring technology, the request of noncontacting measurement is raised for some purposes. The advantages of performing noncontacting measurement by utilizing optical-fiber sensors are their simple structure, small size, anti-electromagnetical field interference, and wide frequency capability. Fig. 1 shows the general principle of the optical fiber noncontacting sensor. The transmission fibers illuminate the test object, and the receiving fibers convey the reflected light to a detector, the output Y is related to the structure parameters of fiber probe S, the reflectivity p and roughness coefficient R. of test object, the distance X, and the illumination power P., i. e.