Multi- and Dual-Wavelength Laser at S-Band by Incorporating All-Fiber Lyot Filter in Tm3+-Doped ZBLAN Fiber: A Millimeter-Wave Generation Toward 5-G Communication

In this work, we have demonstrated the generation of multi- and dual-wavelength fiber lasers at the S-band using an all-fiber-based Lyot filter in a thulium-doped fluoride fiber laser. The Lyot filtering mechanism was first realized at S-band using a polarizer, two polarization controllers, and a 20-m polarization-maintaining fiber. About 13 lasing lines were observed at the S-band covering the wavelength region of 1502 to 1505-nm. The highest possible optical signal-to-noise ratio in a multiwavelength fiber laser was 57.2-dB at the operating wavelength of 1504.52-nm. The stability of this multiwavelength fiber laser was also realized for 2 hours. A highly stable multiwavelength with very slight power fluctuation at lasing peaks of only about ≤ 0.4 dB: there are no wavelength changes during the multiwavelength laser operation for 2 hours. The free spectral range (FSR) of the all-fiber Lyot filter was 0.24-nm, and the frequency bandwidth was achieved as 31.78-GHz. When a tunable bandpass filter (TBPF) was included in the laser cavity, a dual-wavelength fiber laser (DWFL) was also realized at 1504.98 and 1505.22-nm.