A Study Of L-band EDFA

For the increase of wavelength for the DWDM system, we find that it is necessary to expand the C-band to the L-band even to S-band. L-band EDFA is the one of the best choice to meet the requirement, because EDFA has been used widely in the optical communication system and its performance in C-band is excellent. Through building the model of EDFA, the reason of low gain of L-band EDFA and the difficulties of design of L-band EDFA were studied. And the configuration of L-band EDFA using ASE pump source was proved to be effectively to enhance the gain. The wavelength of the ASE pump source was controlled by the Erbium-Doped Fiber, and if the filter added, the wavelength was determinated by the wavelength of the filter. The ASE pump source, the wavelength range of which is from 1520nm to 1530nm, can get the equal gain compared with the configuration of ten 1520nm pump sources. And the performance of L-band EDFA using co-pumping C-band pump source and 980nm LD pump source was studied via experiment and numerical calculation. The model of EDFA was based on the propagation and rate equation of a homogeneous, two-level laser medium and simplified further for the convenience of calculation. And the relationship between gain and other parameters, such as pump power, can be calculated by using the model. The gain of L-band EDFA was calculated by using the "forecast-remedy"mathematics system based on the model, which means: at first, gain and other parameters were calculated without considering ASE power, and these parameters would be used in the infinite subdivision method to calculate the true gain then. As to the ASE power, the infinite subdivision method was useful, too. Finally, the performance of L-band EDFA with the ASE pump source was analyzed theoretically. In the configuration of co-pumping with a conventional 980nm LD and an auxiliary single C-Band, the influence of C-Band power and wavelength on gain of L-Band was analyzed principally. And in the experiments, all the phenomenon proved the influence. In the experiment, with an injection for 6dBm at 1520nm, 6dB of the gain enhancement for –20dBm input at 1590nm was achieved compare with the configuration of double 980nm pump soureces.