Experimental Comparative Study on Gain and Noise Characteristics of All-Fiber Few-Mode Amplifier Under Different Pumping Methods
An all-fiber few-mode erbium-doped amplifier was built to compare the effects of different pump modes and different pump directions on the gain characteristics of the three signal modes,LP01,LP11a,and LP11b. The experimental results show that the amplifier has the best performance under forward LP11 pumping. The signal gain is more than 20dB,the differential modal gain (DMG) is less than 0.9dB and the noise figure is less than 9.6dB in the whole C band. At a sig-nal input power of-10dBm/mode,the gain of all three signal modes at 1550 nm exceeds 20.8dB,the DMG is as low as 0.3dB,the noise figure of LP01 signaling light is lower than 6.2dB,and the noise figure of LP11 signaling light is lower than 9.6dB. Comparing the different pumping directions under the four pumping schemes,it can be found that the noise figure of the for-ward-pumped amplifier is the smallest,but the gains of the three signal modes are also smaller,while the gain of the higher-order signal modes is increased by using the backward-pumped one,but the noise figure will also become larger. Compar-ing the pumping modes,it can be found that compared with the LP01 pumping,the LP11 pumping can significantly increase the gain of the LP11 signaling light,and has less effect on the gain of the LP01 signaling light,which can reduce the DMG value.