Experimental investigation of noise in double-pass erbium-doped fiber amplifiers

In this paper, noise figure characteristics of double-pass amplifiers are investigated. Experimental analysis between single-pass and double-pass amplifications is discussed with 1480 nm pumping scheme. The noise figure penalty of the double-pass amplifier compared to single-pass amplifier is contributed by the generation of amplified spontaneous emission in backward direction with respect to the initial signal direction. Thus, the optical signal-to-noise ratio of the signal is degraded with the same amount of the noise figure penalty.