[2] Pfeiffer T, Schmuck H, Bulow H. Output power characteristics of erbium-doped fiber ring lasers. IEEE Photonics Technol. Lett., 1992, 4(8):847～849

[3] Pfeiffer Th, Bulow H. Analytical gain equation for erbium doped fiber amplifiers including model field profiled and dopant distribution. IEEE Photonics Technol. Lett., 1992, 4(5):449～451