Er3+-doped fiber lasers and amplifiers are receiving a lot of attention in the field of optical communication, due to their high gain at the 1.5 μm region and their low insertion loss. Recently, Laming et. al. reported that a pumping line at 980 nm is promising and obtained a gain as high as 24 dB for 11 mW pump.1 Snitzer et. al. pointed out that 1.48-1.49 μm pumping for the Er -fiber amplifier is advantageous because the wavelength is so close to the laser amplifier wavelengths of 1.53-1.56 μm.
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