| Currently, the video monitoring system consists several small screen displays. It will not only cause monitoring persons'eyes tired, but also cause unpredictable consequence if they distracte when there is an accident.The multi-channel audio and video monitoring system, when the unexpected things happen in some area, can accurately switch the signals automatically to this area. The video image is displayed on the screen and the alarm will be gived. In addition, if all of the audio and video data is stored, we not only need large-capacity storage space, but also have to copy and clear the data regularly. LabVIEW digital sofeware control multi-channel switching to switch multi-channel audio and video signals automatically. So only the audio and video signals of the invasion area are transmitted to the host, and only these signals will be preserved, which will save lots of disk space.The system uses fiber-optic acoustic sensor which has advantages of anti-electromagnetic interference, high sensitivity, corrosion resistance and high stability. It has a strong vitality in a complex electromagnetic environment. The fiber-optic acoustic sensor is based on single-fiber reflective intensity modulation theory. Using light field distribution theory for the multimode fiber, the mathematical models of the single-fiber reflective intensity modulation and sensitivity for fiber-optic acoustic sensor are given. The optimal structural parameters are presented by using MATLAB numerical analysis methods, and the best fiber-optic acoustic sensor design scheme is put forward. According to the sound-machine-electric system equivalence principle, the acoustic impedance equivalence circuit of the sound sensor internal components has been given, then the sensitivity model been gotten too, and the probe of acoustic sensor has been optimizated further. According to the design, the fiber-optic sound sensor physical model has been produced. The optical transmitter, optical receiver and other hardware circuits have been designed, and the multi-channel audio and video monitoring system has been completed. At last, performance test of the monitoring system has been conducted.Results of the system performance test shows that the sensitivity of fiber-optic acoustic sensor is up to about 63.1mV/Pa, which is higher than that of traditional moving coil electromechanical microphone, and the distortion degree of it is less than that of traditional mircophone too. The directional of it is look like a number eight. And it can pick up voice signal at the range of 360 degree. Voice signal can be restored through the audio, and multi-channel audio and video signal can be switched successfully,so the expected goals is achieved. |
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