| 摘要 |
PROBLEM TO BE SOLVED: To realize an improved performance comparable to that of a normal fiber amplifier by an arrangement wherein an optical fiber has a figure of merit higher than a specified value which is the integration in a specified wavelength range of the total wavelength loss of a filter means. SOLUTION: A plurality of L band fiber amplifiers (EDFA) 30 each having a C band removing filter in an Er doped fiber selected to attain an amplifier having a figure of a merit (FOM) higher than 400 dB.nm are arranged. The FOM is the integral of FL (λ) over the wavelength region of 1520-1565 nm and the FL (λ) is the total loss ofλby a C band removing filter at a length L of the Er doped fiber. Several C band removing filters 351, 352, 353 are arranged in the EDF. The upstream filter 351 is located at a specified distance L1 from the input end of the EDF, the filter 352 is located at a specified distance L2 from the filter 351 and the filter 353 is spaced apart by a specified distance L3 from the filter 352. |
