The Amplification Properties of a Highly Er3+-Doped Phosphate Fiber

Abstract
The amplification properties of a highly Er3+-doped phosphate fiber were measured. Gain was observed in the wavelength region of 1.525-1.57 µm and the wavelength at maximum gain was 1.535 µm. Since the absorbed pump threshold obtained experimentally agreed with the calculated result, no cooperative upconversion process occurred in the 1.53 wt% Er2O3 fiber.