| 摘要 |
PURPOSE:To reduce the propagation of high-order modes by providing a 1st core which forms the center part of an optical fiber, a 2nd core which has a lower refractive index than the 1st core, and a clad which has a lower refractive index than the 2nd core. CONSTITUTION:In a sensor part 5 which is stressed to deform, light pulses sent in the optical fiber 4 from the side of an OTDR 3 cause backward scattering to generate optical transmission loss. Consequently, reflected light from the sensor part 5 to the OTDR 3 is reduced and the stress in the sensor part 5 can be detected by the OTDR 3. Namely, the 1st core 6, 2nd core 7, and clad 8 vary in refractive index stepwise, so the difference in refractive index between the 2nd core 7 and clad 8 becomes small and the high-order mode which enters the clad 8 from the 2nd core 7 as the backward scattered light is generated becomes easy to enter the side of the 2nd core 7 again. Consequently, the attenuation of the high-order modes in the optical fiber 4 becomes extremely large. |
