The invention is a device and measuring method for using Brillouin
optical fiber circle
laser to measure linewidth of ultra-narrow
laser, which relates to a measuring device and method for
laser linewidth. The output of the
laser source is connected to the input of the
isolator, the output of the
isolator is connected to the input of the
fiber coupler, the output of the coupler is connected to the inlet of the
fiber coupler, the output of the
fiber coupler is connected to the input of the photoelectric
diode, the output of the photoelectric
diode is connected to the input of the
frequency spectrum analyzer, the fiber
circular cavity is formed by connection one end of the aperture circle made up of unimodular fiber and the port of the
fiber coupler, another end of the aperture circle is connected to the port three of the coupler. The method is: the laser needed to be measured is sent into the fiber circle cavity, when the power of the laser needed to be measured reach the threshold of SBS, it generates a first order Stokes light in the coupler, when the power of the first order stokes light reach the SBS threshold, it generates the second order stokes light in the coupler, then the second order stokes light and the laser needed to be measured frequency are analyzed by the
frequency spectrum analyzer, and the linewidth can be acquired.