Double-pass bidirectional pump broadband L-band erbium-doped superfluorescent fiber source

Abstract

In this paper, a novel double-pass bidirectional pump broadband L-band erbium-doped superfluorescent fiber source (SFS) is demonstrated for the first time. In this fiber source, the EDF is divided into two segments, one of which (EDF2) is bidirectional pumped by a 980nm laser diode through two wavelength division multiplexers (WDM), and the other one (EDF1) is arranged between the reflector and the first WDM. EDF1 is unpumped. The fiber length ratio of the EDF1 length to the total length is defined as R_L=L_EDF1/(L_EDF1+ L_EDF2). The pump power ratio of forward to total pump power of EDF2 is defined as K=P_forward/P_total. The effects of the fiber length and pump power arrangement on the output characteristics of the L-band fiber source are simulated. With an appropriate pump power ratio K and an optimal fiber length ratio R_L, broadband L-band erbium-doped SFS with flat output spectrum can be obtained. Additionally, the optimal fiber length ratio R_L is also depended on the pump power ratio K. When K>0.4, the optimal R_L tends to be changeless. When K=0.1, the optimal R_L is 0 and widest flat spectrum is achieved with a 3-dB bandwidth of 63 nm (1540nm-1603nm).