PM2.5 and PM10 are important indexes reflecting air quality. Based on the MIE angular scattering principle, a PM2.5 and PM10 detector arraywasdesigned,which was miniaturized and all fiber structures. Theoretical deduction and Matlab program simulation were given to illustrate the basic principle of the system. The influence of system parameters on measurement accuracywere discussed, such aslaser wavelength, scattering angle and receiving range parameters. Using optical fiber spherical end face instead of discrete lens group, miniaturization of probe structure was realized. The introduction of frequency modulated continuous wave (FMCW) technology, realization of multi-element frequency division multiplexing. At the same time, the influence of stray light is eliminated and the signal to noise ratio is improved effectively. The system can simultaneously measure the concentration of PM2.5 and PM10 at multiple locations.
Linear cavity optical fiber lasers have the advantages of small size, light weight, stable mode, and easy large-scale multiplexing. However, due to the spatial hole burning effect in linear cavity lasers, the long linear cavity fiber lasers have the problem of multi-mode oscillation. In this paper, the quarter-wave plate made by polarization-maintaining fiber and the special combination of fiber grating are used to control the polarization of light transmitted in different directions, which reduces the hole burning effect and realizes the laser few-mode output. The laser performance test results showed that the structure have obvious effect of eliminating space burning holes,which played an important role in eliminating the space burning hole of the line cavity laser and narrowing the laser line width.
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