| 摘要 |
PURPOSE:To improve measurement precision and to reduce the cost of a device by connecting sensor heads in series and interposing them as a sensor head part between a light source part and a reception part. CONSTITUTION:Light beams outputted by light sources 2a and 2b are multiplexed 18 optically. Sensor heads 5u and 5v are connected in series through a connector 10u, an optical demultiplexer 19, and a connector 4v and heads 5v and 5w are also connected in series through a connector 10v, a fiber 20, and a connector 4w to constitute the sensor head part. Further, the output light of the multiplexer 18 is made incident on the head 5u through the optical fiber 3 and connector 4u. The light output of optical intensity modulation of the sensor head part is demultiplexed 21 optically through a connector 10w and a fiber 11 and supplied to photodetecting elements 12a and 12b. A voltage signal that the element 12a outputs is separated by a receiving circuit 13a into a DC component Vda and an AC component Va; the component Va is inputted to a signal processing circuit 23 through a low-pass filter 22 and the component Vda is inputted to the signal processing circuit 23 directly. Only the DC component Vdb of the element 12b is extracted by a circuit 13b and supplied to the circuit 23.
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