As the TLS is turned off, the unstable self-lasing cavity modes are intrinsically generated and dominate the laser oscillation around 1557–1563 nm owing to the mode competition in EDFL. The mode
competition limits the tuning wavelength range and impacts the power stability of the suggested BEFL. In order to suppress the free-running cavity modes, BP wavelength is required to match with the self-lasing modes wavelength to improve the performance of the laser. Hence, we set BP at a wavelength of 1557 nm.