35-dB gain Tm-doped ZBLYAN fiber amplifier operating at 1.65 mu m

We demonstrate the first high gain rare-earth-doped fiber amplifier operating at 1.65 mu m, It consists of ZBLYAN fiber with a Tm3+-doped core and Tb3+-doped cladding, pumped by 1.22 mu m laser diodes, It is possible to achieve efficient amplification with Tm3+ ions if their amplified spontaneous emission (ASE) in the 1.75 to 2.0 mu m wavelength region is suppressed by doping Tb3+ ions in the cladding, A two-stage-type fiber amplifier is constructed and a signal gain of 35 dB is achieved for a pump power of 140 mW. A gain over 25 dB is realized in the 1.65 mu m to 1.67 mu m wavelength region.