Multiwavelength Mode-Locked Fiber Laser Based on an All Fiber Lyot Filter

We report the experimental demonstration of a multiwavelength passively mode-locked fiber laser based on an all-fiber Lyot filter (AFLF). The Lyot filter is composed of two 45°-titled fiber gratings (45°-TFGs) and a length of polarization-maintaining fiber (PMF). The free spectrum range (FSR) and the 3-dB bandwidth of the Lyot filter are 7.5 nm and 3.6 nm, respectively. The laser generates 5-wavelength mode-locked pulses, which have 7.49 nm channel spacing, 192.6 kHz fundamental repetition rate and over 50 dB signal-to-noise ratio (SNR). As increasing the pump power from 178 mW to 407 mW, the pulse width and the average output power increased linearly from 10 ns to 23 ns and from
$256\mu \text{W}$
to
$621\mu \text{W}$
, respectively. In addition, the fluctuations of center wavelength and laser power are < 0.5 nm and < 0.5 dB respectively within a duration of 1 hour.