Tunable narrow-linewidth fiber laser based on an optically controlled tunable filter

A tunable narrow-linewidth fiber laser based on an optically controlled tunable filter is demonstrated. The filter consists of ytterbium-doped polarization-maintaining fibers (YD-PMF) and polarization-maintaining fibers (PMF), which are fused together with an angle offset of 90 degrees between their fast axes. This allows for the flexible adjustment of the wavelength of the laser by changing the pump power injected into the YD-PMF. A tuning range of 16.99 nm, spanning from 1547.87 nm to 1564.86 nm, has been achieved. The laser's linewidth and optical signal-to-noise ratio (OSNR) are approximately 300 Hz and over 32.38 dB, respectively. Additionally, the fluctuation in wavelength and power of the laser are kept to less than 0.02 nm and 0.14 dB within two hours, respectively.