Flat Multi-Wavelength Brillouin Erbium-Doped Fiber Laser Based on a Sagnac Loop with an Unpumped Erbium-Doped Fiber

We have demonstrated a flat multi-wavelength Brillouin erbium-doped fiber laser (MWBEFL) based on a Sagnac loop with an unpumped erbium-doped fiber (Un-EDF). A Sagnac loop with an Un-EDF is used as power equalizer to achieve multi-wavelength power flatness by adjusting the birefringence beat length properly. The experiment result of Brillouin Stokes lines output power flatness is ±0.315 dB and optical signal-to-noise ratio (OSNR) is 18.97dB within 33 nm range from 1532.0 nm to 1565.0 nm. The flatness varies from ±0.315 dB to ±1.38 dB and average OSNR is about 17.51 dB. The peak power of Brillouin stokes lines under different wavelengths are extremely close and its fluctuation range is about ±0.37 dB. The experimental result is close to our previous experimental value using a passive Sagnac loop with an Un-EDF. The flat range covering almost the entire C-band has a broader application prospect in high-sensitivity distributed optical fiber sensing and wavelength division multiplexing