| 摘要 |
<p>An optical fiber sensor for detecting a change of an external subject (50, 88, 90), based on measuring and reference beams. The sensor includes an optical fiber (24) or fibers (328, 334) for optically coupling a light transmitter/receiving portion (100, 100 min , 100 sec ) and a sensor head portion (102, 102 min , 102 sec ). Where the measuring and reference beams are transmitted through the single optical fiber (24) to the sensor head portion (100) in respective two transmission modes having mutually perpendicular polarization planes, the sensor head portion may include a Faraday effect element (44) for rotating the polarization planes of the measuring and reference beams, in order to switch the two transmission modes when the beams are returned through the fiber to the transmitter/receiver portion. Where the measuring and reference beams are transmitted to the sensor head portion by the respective first and second fibers (238, 334), the sensor head portion (100 sec ) may employ a device (354, 360) for directing the two beams so that the measuring and reference beams are returned to the transmitter/receiver portion (100 sec ) through the second and first fibers.</p> |
