Research On Cavity-assisted-pumping Highpower Er³⁺/Yb³⁺ Co-doped Optical Fiber Amplifier

The output of high power Er³⁺/Yb³⁺co-doped fiber amplifiers?EYDFAs?is a light wave at around 1.5?m.The laser light at this band not only has low loss propagating in fibers and in the atmosphere,but also has a relatively good eye safe characteristics.Due to these advantages,high power EYDFAs have important application values in many fields like photo-communication,military,healthcare etc..The previous studies show that the amplified spontaneous emission at Yb-band is a vital factor restraining the output power of EYDFAs.To solve that problem,we put forward a new method for suppressing the Yb-ASE named the Yb-cavity-assisted method,and established a theoretic model for it.Moreover,we made detailed research with numerical and experimental methods.The main research contents in this paper are as follows:1.We proposed a new method for the suppression of the Yb-ASE named the Yb-cavity-assisted method.Based on the theoretic model of an ordinary EYDFA,we revised the boundary conditions after considering the introduction of an assisted cavity.We established a theoretic model for the cavity-assisted-pumping EYDFAs,and put forward a highly-efficient stable algorithm for solving that,named the boundary conditions modified algorithm.The program was compiled in Matlab as well.2.Based on numerical simulation,we made systematic theoretic studies on the cavity-assisted-pumping EYDFA,during which we investigated on the parameters that influence the performance of an EYDFA,including the oscillation wavelength of the cavity,the pump direction and pump power,and the wavelength of the signal.And we compared the Yb-cavity method with the Yb-signal method,which had been reported before.The results showed that the Yb-cavity method is superior in efficiency improving,fiber length shortening,stability improving and gain flatness optimizing.3.We experimentally studied and carefully analyzed the output characteristics,the spectrum characteristics,and the gain characteristics of the cavity-assisted-pumping EYDFA.In our experiment,a diode laser at 976nm was used as the pump source.At a pump power of 17W,the¹00mW signal at 1550nm was amplified and the output power turned out to be 7.25W.Moreover,the slope efficiency was 45.6%,the OSNR was 50.6dB,and the gain flatness between 1534nm-1568nm was 0.12dB.4.The results show,that the Yb-oscillation in the assisted cavity can effectively suppress the Yb-ASE and its self-oscillation by correctly choosing the Yb-band resonant wavelength and optimizing the fiber length.And with the resorption of the Yb-oscillation by the assisted cavity,more energy could be transferred to Er signal,improving the efficiency remarkably.So,cavity-assisted-pumping is a promising method that can obtain the high output of an EYDFA.