| 摘要 |
PURPOSE:To photodetect Stokes light which is diffracted or passed and to improve the logical efficiency of a measuring instrument by simple constitution by allowing back scattered light with specific wavelength which is diffracted by or passed through a diffraction grating or prism and projected from an end surface of an optical fiber provided on an optical axis to enter the diffraction grating or prism reversely. CONSTITUTION:Light from a light source 1 is made incident on the reflection type diffraction grating 10 (or prism) at an angle theta0 to a normal 11 and light with center wavelength lambda0 which is reflected or diffracted at an angle theta1 and projected is made incident on the optical fiber 4. The Stokes light (wavelength lambda0+a) of the rear scattered light which is projected from this optical fiber 4 is made incident on the grating 10 at the angle theta1 and made incident on a photodetector 7 for Stokes measurement on the optical axis while having the projection optical axis at an angle -theta2 to the normal 11 because of the difference in wavelength from the incident light to the fiber 4. Similarly, anti-Stokes light from the fiber 4 is measured by a photodetector 9 for anti-Stokes light. |
