| 摘要 |
PURPOSE:To make it possible to obtain a flow speed meter with high accuracy, by using a polarization surface preserving optical fiber connected to a Faraday element at one end thereof and to a fluid to be measured at the other end thereof. CONSTITUTION:Light from a light source 1 is subjected to linear polarization through a polarization plate 2 to be connected to the optical axis of a polarization surface preserving optical fiber 4' by a lambda/2 plate 3. Linearly polarized light emitted from the fiber 4' is permeated as the P-wave of a polarization beam splitter 5 and further inclined 45 deg. by a Faraday element 6 to be connected to the optical axis of a polarization surface preserving optical fuber 4. There are two kinds in light returing from the leading end of the fiber 4 against light propagating to the leading end thereof and the first one is light reflected at the leading end of the fiber 4 while the second one is light scattered by a fluid 8 in the vicinity of the leading end of said fiber 4 and generates a frequency shift amount wherein a wavelength is proportional to a flow speed. These reflected lights are further rotated 45 deg. by the element 6 and reflected by the splitter as a S- wave to be received by a light receiver 7. By calculating the frequency shift amount in this receiver 7, the flow speed of the fluid is calculated. |
