Contents I. Introduction
Dual-wavelength fiber lasers based in Tm-doped fibers (TDF) operating at the 2- wavelength range have been received increasing attention in laser researches due to their great potential applications in optical communication, light detection and ranging (LIDAR), optical signal processing, microwave photonics, terahertz generation, and optical instrumentation. In this sense, dual-wavelength generation of all-fiber Tm-doped fiber lasers (TDFLs) has been increasingly achievable as compatible fiber components become readily accessible. Recently, different dual-wavelength TDFLs approaches at the 2- wavelength band were reported. These configurations are based on fiber Bragg Gratings (FBG) [1]–[9], spatial mode beating effect [10]–[12], carbon nanotubes [13], photonic crystal fibers [14], and fiber interferometers [1], [15]–[17], among others. Liu et al. reported the single-polarization dual-wavelength generation of a TDFL based on a polarization maintaining (PM) FBG and a PM Fabry-Perot filter [1]. Zhou et al. proposed a stable dual-wavelength TDFL based on cascaded fiber Bragg gratings [6]. Soltanian et al. achieved stable dual-wavelength operation of a TDFL operating at by using a 10 cm length of photonic crystal fiber [13]. Nevertheless, most of the previously reported dual-wavelength fiber lasers based on TDF exhibit laser emission with wavelengths below of .
