Switchable narrow line-width dual-wavelength erbium-doped fiber laser using cascaded multi-mode Bragg gratings and high fineness filter

A switchable narrow line-width dual-wavelength erbium-doped fiber laser using cascaded multi- mode Bragg gratings incorporating a novel high-finesse ring filter was proposed and demonstrated. The ring filter was a ring filter composed of two optical couplers and a section erbium-doped fiber. Thanks to the gain generated by the erbium-doped fiber, the ring filter has a high fineness spectral. The incorpora- tion of the ring filter led to the suppression of undesirable modes in the dual-wavelength erbium-doped fiber laser (EDFL). An experiment was carried out, in which six kinds of narrow line-width dual-wave- lengths combination were generated. And 3 dB linewidth of each wavelength of 0.14 nm to 0.16 nm without the filter was narrowed to 0.05 nm with the high fineness filter.