| 摘要 |
PROBLEM TO BE SOLVED: To measure the critical incidence angle and the refractive index for an optical fiber by peacing the optical fiber where a protection coat covering is partially or entirely stripped and measuring transmission intensity when light is applied to the optical fiber. SOLUTION: An optical fiber 1 is composed of a core 9 and a clad 10. In a general optical fiber, the outside of the clad 10 is subjected to protection covering, and laser beam from a light source enters at a low angle where it is not diffused greatly, so that nearly entire incident light is totally reflected by the boundary surface between the core 9 and the clad 10 and is transferred into the core 9. When the outside protection covering of the optical fiber is released and hence the outside of the clad 10 is brought into contact with liquid to be measured, incidence light from a dispersion light source becomes a beam being totally reflected by interface between the clad 10 and a measurement container 4 as in a beam A-A' when the angle of incidence becomes larger in addition to other beams being propagated in the core 9.
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