Tunable Fiber Laser With Ultra-Narrow Linewidth Using A Tunable Phase-Shifted Chirped Fiber Grating

We experimentally demonstrate a tunable $C$ -band erbium-doped fiber ring laser with ultra-narrow linewidth using a tunable phase-shifted linearly chirped fiber Bragg grating (PS-LCFBG) as an intracavity ultra-narrowband filter. The center wavelength of the PS-LCFBG with an ultra-narrow bandwidth of ${≪}$10 pm is thermally tuned by scanning a current-controlled resistance wire along its length. The laser has an ultra-narrow linewidth of ${≪}$1.52 kHz, a tuning range of ${sim}$ 15.5 nm, a good sidemode suppression ratio of ${>}$30 dB, an output power of ${sim}$10 dBm, a small power variation of ${≪}$ 0.2 dB, and a small wavelength variation of ${≪}$0.01 nm. The laser structure is simple and cost-effective.