The Design And Realization Of Narrow-linewidth Semiconductor Laser Linewidth Measurement System

Narrow linewidth semiconductor laser is widely used in fields of optical measurements and optical communications. In many systems, such as all fiber velocity interferometer and fiber carrier wave transmission systems, the character of laser linewidth determines the accuracy of the system.In this paper, the radiation mechanism and spectrum characteristics of single-longitudinal-model semiconductor laser is analyzed. Based on Mach-Zehnder interference structure, a delayed self-homo-dyne linewidth measurement system with high precision, simple structure and wide range of application is designed. By analyzing the connection between the spectrum of photocurrent and the spectrum of the laser, as well as the length of the fiber and so on the photo-detector performance, specific programs are discussed, and the method of short fiber self-homo-dyne linewidth measurement is put forward. Software is used to replace the traditional hardware, spectrum analyzer, making the structure of the instrument more compact, and the cost of the system also has been reduced. Finally, the mathematical tool Matlab is used to validate the program. Based on the simulation results, the instrument with a delayed length of 500m has been set up and a single-longitudinal-model DFB semiconductor laser of the laboratory whose wavelength is 1550 nm and the linewidth is 160Khz has been tested by the instrument. The result is 152.6Khz, and is in an ideal framework and proved the superiority of the linewidth measurement system in fields of narrow linewidth measurement.