| At the present stage, the signal transmission between high voltage and low voltage mainly rely on metal wire, not only the accuracy will be reduced because of electromagnetic interference in high voltage environment, but also may result in equipment damage and casualties because of the high voltage and large current is introduced to the low voltage side, if the protection measures are improper or fault. In this paper, the traditional metal wire is replaced by fiber and the electrical signal is replaced by optical signal. By this way, the transmission and isolation of the signal is completed.In this paper, by comparing the three modulation modes and their characteristics of the light source on the basis of the analyzing optical fiber communication and signal transmission.For DC signal and AC signal, the frequency modulation and direct intensity modulation are used.In the design of fiber isolation-transmission device for DC signal based on voltage frequency modulation, the V-F conversion circuit was comprised by using LM331, and the simulation test is carried out. In addition, light source and photoelectric detection device are screened, the driving circuit of the light source and the receiving circuit of photoelectric detection device are designed.In the design of fiber isolation-transmission device for AC signal based on intensity modulation, different operational amplifiers are used to different links. The driving circuit of light source and photoelectric conversion circuit are also designed. Test for AC signal transmission is carried out by using the device that is designed. Tests and analysis show that the fiber isolation-transmission device designed in this paper has less error, fast speed, 1MHz bandwidth. It can be used to realize the transmission and electrical isolation of 5V sinusoidal signal with different frequencies. |
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