Systems and methods are disclosed for amplifying optical signals in the 850 nm window. In one embodiment, an amplifier system includes a span of Thulium-doped fiber (TDF) and two pump systems. The TDF span receives and transports optical signals in the 850 nm window. A first pump system pumps the TDF span at a wavelength in the range of 1390 nm to 1430 nm, and a second pump system pumps the TDF span at a wavelength in the range of 670 nm to 720 nm. The pumping generates gain in the optical signals in the 850 nm window. In another embodiment, the amplifier system includes a single pump system. The pump system pumps the TDF span at a wavelength in the range of 1390 nm to 1430 nm to generate gain in the 850 nm window.