We demonstrate significant gain over 1470–1540 nm in a thulium doped silica fiber amplifier. The fiber is compatible with standard fabrication techniques, and can be fusion spliced to standard telecommunications fibers.
A complete experimental and theoretical study of rare earth doped fiber-optic amplifiers for the first tele-communication window has been made. The thulium doped fluoride fiber amplifier is shown to provide amplification in the 800nm-820nm signal region. A complete steady state theoretical model has been presented and the model has been experimentally verified. The model predicts the gain, noise figure and the amplified spontaneous emission in the 800nm, 1470nm, 1900nm and 2300nm bands. The effect of population trapping at the sp3Fsb4 energy level of thulium ion is also shown with the help of the model. It has been shown that about 5-15%o of the population is trapped at the sp3Fsb4 energy level. We have also shown theoretically, the expected gain and noise performance of Thulium doped fluoride fiber amplifiers pumped in the 680nm absorption band. The maximum gain at 806nm is slightly lower than with comparable 780 nm pumping. The gain bandwidth is however found to increase with 680nm pumping. The higher ASE at shorter wavelengths ($<$806nm) reduces the gain at the peak wavelength (806nm). This is a result of the better inversion with three level pumping at 680nm as compared to two level resonant pumping at 780nm. We report an efficient single mode erbium doped flouride fiber amplifier in the 850nm signal band for the first time. The amplification is through an up-conversion process. The erbium doped flouride fiber amplifier was pumped with an estimated pump power of 35mW at 792nm. We have also considered a theoretical model for a single mode erbium doped fluoride fiber amplifier. Efficient amplification occurs because of the strong excited state absorption at the pump wavelength from the sp4Isb13/2 energy level.
S-band ground state absorption in a thulium-doped fiber amplifier (TDFA) has been studied in detail experimentally and theoretically. While traditionally considered difficult to measure, its presence is shown to have significant impact on amplifier power excursion during dynamic wavelength add-drop, due to the energy transitions inherent to the Tm/sup 3+/ ion. For specific pumping scheme and operating conditions, gain increases with increasing signal input, a behavior significantly different from conventional three-level optical amplifiers. Numerical models are presented that correctly account for these phenomena. This promises to provide insight for gain control algorithms for TDFAs under bursty traffic conditions in a future reconfigurable wavelength division multiplexed environment.