Research On Intelligent Tuning Of Fiber Bragg Gratings External Cavity Semiconductor Laser

The wavelength tuning of fiber grating external cavity semiconductor lasers is researched in the paper. Fiber grating is coupled with semiconductor laser which wavelength is 1534.88nm. The laser is extra-long external cavity and weak feedback. The narrow line-width and tunable output wavelength is realized in the experiment.At first, the theory of semiconductor laser is introduced in this paper. The present state and the trend in development of lasers are summarized. And the theoretical analysis of the compound cavity of a semiconductor laser with external optical feedback is conducted. Line-width narrowed by a grating as optical feedback component is studied as well as the conditions of continuously tuning the wavelength. The external cavity semiconductor laser is researched on theory and experiment. The tuning device allows the laser to be tuned in a range of 1.5nm. And line-width is to be reduced. The effects of external-cavity length, injection current and temperature to the output of laser are also analyzed. A stepping motor is applied in the tuning system. By control of the angular displacement of stepping motor, we can modify the centre wavelength of FBG.. In the paper, the hardware design circuit and program flow diagram are demonstrated. By the use of coupler, 30% laser is injected into the semiconductor laser, 70% laser is outputted. In our experiment, many output wavelengths can be obtained, such as 1534.50nm, 1534.57nm and 1534.80nm. The line-width is 0.061nm. The side mode rejection ratio is 49.771dB. The frequency stabilization is less than 6.5×10^-7.