| 摘要 |
<p>An optical fibre amplifier can maintain its optical power output above a level exceeding +20dBm and a low noise figure if the input optical signal shows a high power level. It comprises a front stage amplifying optical fibre 11 doped with a rare-earth element and arranged in a front stage 10A thereof and a back stage amplifying optical fibre 12 also doped with a rare-earth element and arranged in a back stage 10B thereof, wherein the front stage amplifying optical fibre 11 is provided at the signal light input terminal 13 thereof with a first optical coupler 14 for coupling signal light and excitation light in a same direction and at the signal light output terminal 15 thereof with a second optical coupler 16 for coupling signal light and excitation light in opposite directions and the back stage amplifying optical fibre 12 is provided at the signal light input terminal 19 thereof with a third optical coupler 21 for coupling signal light and excitation light in opposite directions, the first, second and third optical couplers 14, 16 and 21 being connected respectively to a first excitation light source 17 for generating excitation light with the 1,480nm wavelength, a second excitation light source 18 for generating excitation light with the 980nm wavelength and a third excitation light source 22 for generating excitation light with the 1,480nm wavelength. <IMAGE></p> |
