Research On Phase Noise Extraction For Laser Linewidth Measurement System At 2?m Band

2?m band fiber laser has shown significant application prospects in medicine,optical telecommunications,ultrafast optic,remote sensing,radar and biomedical fields because of its band characteristics.The narrow-linewidth output laser in this band can also exert greater advantages in the field of free space optical communications,and has a broad application prospect.An output-stabilized narrow linewidth laser source and its performance characterization method are indispensable for the research of 2?m band space optical network.However,there is currently no device that can measure the laser at this band.Therefore,it is of great academic significance and application value to build a set of laser linewidth measurement system for 2?m band.This article mainly completes the following work for the measurement of laser linewidth at 2?m band:(1)The mechanism of laser linewidth measurement using unbalanced interferometer method based on a 3×3 coupler was studied.The phase noise of the output laser was obtained by an unbalanced interferometer,and the linewidth was measured according to the output characteristics of the unbalanced interferometer and the phase noise method.The basic principle is to use mathematical methods to process the interferometer detection data,then obtain the power spectrum characteristics of the phase noise,and the laser linewidth from the calculation;(2)Using wavelet noise reduction,phase demodulation algorithm optimization,wavelet spectrum analysis instead of the traditional Fourier spectrum analysis method,the error caused by the mathematical algorithm of the probe data is corrected,thereby improving the measurement accuracy;(3)A single-longitudinal-mode Thulium-doped fiber laser based on a saturable absorber was established.A 2?m-band laser linewidth measurement system was established.The linewidth of the Thulium-doped fiber laser was measured by the linewidth measurement system by using the optimized algorithm.