| 摘要 |
PURPOSE:To easily detect the occurrence of abnormality by spirally winding an optical fiber round a spacer polygonal in section so that transmission loss is easily caused by external force. CONSTITUTION:An optical fiber 1 is spirally wound round a spacer 2 in a line sensor 5. As the optical fiber 1 is spirally wound round the spacer 2, when lateral pressure P or tension Q generates, compression or tension is generated in the line sensor 5, which causes a very small amount of bending in a portion of the optical fiber 1 that contacts the spacer 2 to increase transmission loss. Accordingly, transmission loss of the optical fiber is caught by a photo detecting element, and an alarm is given by an alarm circuit. Thus, the occurrence of abnormality can be easily informed. |
