Intracavity ranging enabled by a single-frequency self-sweeping fiber laser with a few-longitudinal-mode range.

Self-sweeping fiber lasers have carved out numerous applications such as spectral detection, fiber sensor, etc. In this work, we propose a single-frequency self-sweeping fiber laser with a few-longitudinal-mode range by employing a length of space path to achieve the function of intracavity ranging. Different from the previous design, a fiber collimator and mirror are utilized to act as the reflector, and the distance between them can be adjusted flexibly. Based on this design, we achieve a few-longitudinal-mode self-sweeping operation containing seven longitudinal modes. When the distance is set as a fixed value, the behaviors of fiber laser containing central wavelength, quasi-continuous wave pulse, as well as radio frequency spectrum at different pump power are measured. The intracavity ranging systems are also demonstrated at different distances between collimator and mirror, showing a promising accuracy. This work provides a new laser ranging tool and opens up the applied scenario of self-sweeping fiber laser.