| 摘要 |
A rare-earth metal doped fibre (1) of small radius for use in an optical amplifier or fibre laser. The fibre (1) has its inner core (3) doped with a rare-earth metal so as to have a high Numerical Aperture. The outer core (4) has a low Numerical Aperture and surrounds the inner core (3). A cladding (2) surrounds the outer core (4). |
