| 摘要 |
PURPOSE:To make it possible to improve an S/N ratio, by providing a reference optical fiber and a measuring optical fiber at the same place so that both fibers receive the same external noise, thereby removing the external noise effects. CONSTITUTION:A reference optical fiber 4 and a measuring optical fiber 3 are enclosed in one cable 6 from a light source part 1 to a holding table 2'. Both optical fibers 3 and 4 are fixed to the holding table 2' of an optical fiber sensor 2. Both optical fibers 3 and 4 are enclosed in one cable 7 and taken out. A sensor part 3' of the measuring optical fiber 3 is arranged in, e.g., a zigzag pattern as shown in the Figure, wherein the change in optical length due to temperature and strain is yielded in a large extent. Meanwhile, a part 4' of the reference optical fiber 4, which is fixed to the holding table 2' is very short. Therefore, the effect of this part 4' on the measurement can be neglected. As a result, the effect of the external noises is not present in the phase difference between the light beams from the optical fibers 3 and 4. The adverse effect of the external noises on the measured value in an interference detecting part can be removed and an S/N ratio can be improved. |
