Wavelength interval adjustable multi-wavelength mode-locked erbium-doped fiber laser with high-order mode output

We propose and experimentally demonstrated a wavelength interval adjustable multi-wavelength mode-locked erbium-doped fiber laser (EDFL) cooperated by improved Sagnac comb filter, nonlinear amplifying loop mirror (NALM) and a homemade mode selective coupler (MSC). The improved Sagnac comb filter is worked as wavelength selective filter and the NALM is utilized as saturable absorber to achieve pulse operation. The maximum output wavelength number of nine and tunable wavelength interval of the integer times of 0.5 nm and 1.5 nm are realized in this proposed fiber laser. The mode-locked pulse performance with 101.4 MHz pulse repetition frequency, 5.7 ns pulse duration and 9.86 ns pulse interval are obtained under 100 mW pump power. In addition, LP31 mode with higher than 95 % mode purity is obtained by the homemade MSC. Therefore, the proposed fiber laser can be applied in optical sensing system and mode division multiplexing.