Broad-range self-sweeping single-frequency linearly polarized Tm-doped fiber laser

We experimentally demonstrate a linearly polarized Tm-doped fiber laser with sweeping range up to 26 nm in the region of 1.92 μm. The main feature of the laser is generation of periodic microsecond pulses in which each contains practically only single longitudinal mode radiation. The laser frequency changes from pulse to pulse with high linearity by one intermode beating frequency of the laser ∼8 MHz. The developed source is applied to measure spectrum of water absorption lines in air.