| 摘要 |
PURPOSE:To measure beat length precisely in a short time by making the clad of a beat length measurement part of an optical fiber less in thickness at least partially in a circumferential direction and making the measurement. CONSTITUTION:Laser light is incident from a laser light source 12 to one terminal a single-mode optical fiber 10 through a polarizer 14, lambda/4-wavelength plate 16, polarizer 16', and objective 18 and light projected from the other terminal is guided to a photodetector 22 through an analyzer 20. The beat length is measured by observing leaking light in the lateral direction of the optical fiber 10. The clad 10B of the optical fiber 10 is made less in thickness over the entire circumference at the beat length measurement part or cut partially to take a measurement by a camera 26 or the eye through the thickness-reduced part 10a. Light propagating in a core 10A and the clad 10B decrease in quantity according to an exponetial function and as the clad 10B is thinner and thinner, the quantity of leaking light is made greater. |
