In this paper, a novel non-contact optical measurement method based on the principle of laser self mixing interference for measuring liquid concentration is proposed. The optical path difference caused by changing the concentration of the solution, we found the phenomenon of waveform separation in the laser self-mixing vibration signal. In this system, simulation results of different solution concentrations are obtained based on the feature that each longitudinal mode is independent and do not interfere with each other in the multi-longitudinal mode laser, which successfully verified the corresponding relationship between the degree of waveform separation and the concentration of the solution.
Long-wave infrared wireless communication has much advantage over short-wave infrared. In this paper, the bit error rate performance of LWIR by DPIM is analyzed. The intensity fluctuations of the optical signal are modeled by log-normal distribution, the intensity attenuations are modeled by empirical formula of fog. The system noise includes generation-recombination noise and thermal noise typically for Photoconductive HgCdTe detector. The numerical results of BER are presented. The results illustrate the BER depends on the turbulence strength, bit rate, optical power and link length.
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