Active gain-slope compensation of EDFA using thulium-doped fiber as saturable absorber

In erbium doped optical fiber amplifiers (EDFAs) used in modern high-capacity wavelength division multiplexing; (WDM) systems, the gain flatness of EDFA is very important. in wide-band long-haul systems. In the EDFAs using the passive gain equalizers, the gain flatness deteriorates due to gain-tilt when the operating condition of the EDFA changes, while the EDFAs should maintain the gain flatness even if the operating condition has changed. To solve this problem, we have developed an active gain-slope compensation technique of an EDFA using a thulium-doped optical fiber (TDF) as a saturable absorber. The actively gain-slope compensated EDFA with the TDF compensator keeps the gain profile constant for the wide gain dynamic range more than 8 dB with the low noise figure less than 6 dB in the wavelength range of 1539-1564 nm.