Numerical Investigation of the ASE and Power Scaling of Cladding-Pumped Er–Yb Codoped Fiber Amplifiers

The influence of the amplified spontaneous emission (ASE) on the performance of high-power, cladding-pumped Er-Yb codoped fiber amplifiers (EYDFAs) are investigated numerically. The results show that the counter-pump-propagating Yb-band ASE is the main reason that limits the efficiency of an EYDFA at high pump power. By introducing a co-pump-propagating Yb-band signal at proper wavelength, the counter-pump-propagating Yb-band ASE can be effectively suppressed and thus the available power of the EYDFA can be remarkably improved. This method is also helpful to improve the stability of high power EYDFAs.