We demonstrate a simple dual wavelength ring erbium doped fiber laser operating in single lon gitudinal mode (SLM) at room temperature. A pair of reflection type short period fiber Bragg gratings (FBGs), which have two different center wavelengths of 1545.072 and 1545.284 nm, are used as the wave length selective component of the laser. A segment of unpumped polarization maintaining erbium doped fiber (PM EDF) is acted as a narrow multiband filter. By turning the polarization controller (PC) to enhance the polarization hole burning (PHB), the single wavelength and dual wavelength laser oscillations are observed at 1545.072 and 1545.284 nm. The output power variation is less than 0.6 dB for both wavelengths over a five minute period and the optical signal to noise ratio (OSNR) is greater than 50 dB. By beating the dual wavelengths at a photodetector (PD), a microwave signal at 26.44 GHz is demonstrated.
A wavelength-tunable single-longitudinal-mode (SLM) narrow-linewidth thulium/holmium co-doped fiber laser (THDFL) was developed in this study. The lasing wavelength was determined by combining a phase-shifted fiber Bragg grating (PS-FBG) and a uniform FBG (UFBG). SLM oscillation was achieved by incorporating a dual-coupler ring filter with the PS-FBG. At a pump power of 2.0 W, the THDFL exhibited excellent SLM lasing performance with a stable optical spectrum. It operated at an output wavelength of ~2050 nm with an optical signal-to-noise ratio of >81 dB, an output power fluctuation of 0.15 dB, a linewidth of 8.468 kHz, a relative intensity noise of ≤−140.32 dB/Hz@≥5 MHz, a slope efficiency of 2.15%, and a threshold power of 436 mW. The lasing wavelength tunability was validated experimentally by stretching the PS-FBG and UFBG simultaneously. The proposed THDFL had significant potential for application in many fields, including free-space optical communication, LiDAR, and high-precision spectral measurement.
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