Thulium-doped fluorotellurite glass fibers for broadband S-band amplifiers.

We demonstrated broadband S-band (1460-1530 nm) amplification in Tm-doped fluorotellurite glass fibers (TDFTFs) by using a 1400/1570 nm dual-wavelength pump technique. TDFTFs based on TeO-BaF-YO (TBY) glass were fabricated by using a rod-in-tube method. For an input signal power of 0 dBm (or 1 mW), a broadband positive net gain ranging from <1440 nm to 1546 nm was achieved in a 1.55-m-long TDFTF with a Tm doping concentration of ∼4000 ppm, as the pump powers of the 1400 nm and 1570 nm lasers were 1.7 W and 0.14 W, respectively. The corresponding bandwidth for a net gain of >20 dB was ∼66 nm (1458-1524 nm), and the measured saturated output power was ∼24.84 dBm at 1490 nm. In addition, numerical simulation was performed by using the parameters of the TDFTFs and the pump lasers, and the noise figure was calculated to be <5.6 dB in the S band. Our results showed that the TDFTFs were promising gain media for constructing efficient broadband S-band fiber amplifiers.