| 摘要 |
PURPOSE:To measure a mode double refractive index, to shorten measuring time, and to improve measuring accuracy by changing a wavelength of a light source and also utilizing reflection without varying a length of a fiber to be measured. CONSTITUTION:Light from a wavelength variable light source 7 is converted to parallel light by a lens 8, and converted to intermittent light by using a chopper 9. The parallel light is linearly polarized by a polarizer, and made incident on a polarized wave maintaining optical fiber to be measured 3 through a condenser lens 13. Light reflected by the end face of the condensing lens 13 and the incident end of the optical fiber 3 passes through the polarizer 2 as it is, but light reflected by the emitting end of the optical fiber 3 becomes an elliptic polarized wave. When this refected light passes through the polarizer 2, the optical path is deflected, and it is led to a photodetector 10. When a double refraction axis of the optical fiber 3 coincides with a plane of polarization of an incident light, the detected light becomes the minimum. Therefore, the plane of polarization of the incident light is constituted so that it is made incident on a double refraction axis of the optical fiber 3 at an angle of about 45 deg., and a photodetecting power of the detector becomes the maximum. In this way, measuring accuracy of three digits is obtained.
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