Tench, R.E.R.E.TenchRomano, C.C.RomanoWilliams, G.M.G.M.WilliamsDelavaux, J.-M.J.-M.DelavauxRobin, T.T.RobinCadier, B.B.CadierLaurent, A.A.Laurent2022-03-052022-03-052019https://publica.fraunhofer.de/handle/publica/25831010.1109/JLT.2019.28949732-s2.0-85062853927We report the experimental demonstration and record performance of two-stage broadband, high gain polarization-maintaining (PM) Ho-doped fiber amplifiers (HDFAs) at a signal wavelength of l s = 2051 nm. We begin by presenting a new PM Ho-doped fiber with core diameter 8 mm, a PANDA structure, a cutoff wavelength of 1650 nm, and a peak absorption of 57 dB/m at 1951 nm. Next, we consider architectures for high gain PM HDFAs. Here we demonstrate G = 60 dB with a dynamic range of >40 dB and noise figures as low as 10 dB. We then investigate configurations for high output power PM HDFAs. With one stage, we measure P out = 3.45 W and an optical-optical slope efficiency i = 69%. With two stages, we obtain P out = 6.7 W and i = 80%. The potential bandwidth of the high power PM HDFA is BW = 100 nm (7.5 THz). An optical signal-to-noise ratio of 58 dB/0.1 nm is achieved, and the polarization extinction ratio is >20 dB. Initial comparisons of simulations of gain and output power with our experimental results show relatively good agreement.en004535670journal article