Numerical investigations of double pass, highly selective FBG based DFB-EDFA system for enhanced gain and ASE-mitigation

In this study, we investigate the influence of Distributed Feedback (DFB) lasers on the performance of Erbium-Doped Fiber Amplifiers (EDFA) and explore the EDFA system using coupled mode equations. Our primary objective is to minimize amplified spontaneous emission (ASE) while maintaining a high gain (G). Key factors affecting gain, such as pump power (P_p), erbium doping radius (R_d), EDFA length (L_EDFA), and input signal power (P_s), are analyzed analytically. We examine the propagation behaviour of ASE, gain trends, population inversion, pump signal, and input signal. To mitigate ASE, Fiber Bragg Grating (FBG) is employed. The DP-FBG EDFA configuration demonstrated a gain improvement of 3 dB and a reduction in ASE power by approximately 4 dBm compared to the SP-EDFA configuration. Further comparisons were made across different wavelengths in the C-band, revealing that the optimized EDFA-FBG configuration outperforms the initial setup. Further, out of all the four lasers in C-band, 1550 nm DFB laser maintains Q-6 for longer fiber length with an EDFA having L_opt of 10.52 m, R_d-opt of 2.2 µm and P_sat of − 22.43 dBm. Additionally, the quality factor was assessed, showing that the optimized configuration maintains a higher quality factor. Notably, using FBG as a filter allowed the maintenance of Q-6 over 100 km, whereas an inverted Gaussian filter sustained Q-6 only over 40 km.