Noise characteristics of erbium-doped fiber amplifier pumped at 980 nm

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Abstract
A noise figure of 2.9+or-0.4 dB, measured in a high-gain erbium-doped fiber amplifier for input signals in the range -35 to -15 dBm and for pump powers of >5.8 mW, is discussed. The spontaneous emission factor n/sub sp/ was 0.99+or-0.09 for input signals less than -15 dBm. These low figures are attributable to the optimized fiber design and the use of a pump wavelength of 980 nm, at which erbium operates as a true three-level system. These two factors contribute to the very low ( approximately 500 mu W) pump threshold seen in fiber, which permits nearly complete inversion to be achieved for the low pump powers employed.