| 摘要 |
According to the invention, the intermediate sheath (13) is formed by assembling longitudinal elements (13A) and includes: a first optical material, the refractive index of which differs from the refractive index of the monomode core by at most 10-3; and a second optical material, the refractive index of which is lower than the refractive index of said monomode core and differs therefrom by at least 10-3. |
