Acousto-optic Modulator Driving Source And Audio Demodulation Technology

The emergence of laser has opened up a new era for optical communication and technology.For decades,optical modulation using laser as the carrier has been widely studied.The acousto-optic modulation technology is applied to free-space optical communication,screen display and heterodyne interference detection technology because of its simple structure and good modulation effect.With the development of the manufacturing of acousto-optic devices,the performance of the modulator can meet the precision requirements of various acousto-optic technologies and it promotes the development of the technology.For the widely used Bragg acousto-optic modulators,the paper proposes a linear voltage compensation technique to complete the modulation of the driving power of the acousto-optic modulator so that the acousto-optic modulator can achieve linear control of the intensity of the first-order diffracted light.In this paper,based on the traditional Bragg acousto-optic modulator's RF drive circuit,a kind of digital drive power is designed.The digital drive power is controlled by the FPGA and can generate voltage compensation signals to amplitude-modulate the high-frequency carrier.Through the statistical experiments on the working curve of the acousto-optic modulator,the diffracted light intensity is divided into 48 levels.Linear compensation voltage values??are obtained by the linear regression equation.The linearly compensated diffracted light intensity changes linearly with the control voltage level.In addition,while achieving the output digital modulation voltage,the digital driving power also has the function of outputting the standard periodic signal and analog-to-digital conversion,which makes the digital driving power have more extensive application value.The performance of digital drive power is tested in heterodyne interference detection and voice-signal communication,and an opticalsignal demodulation circuit is designed for the intensity modulation in the audio range.The experimental results show that the linear correlation coefficient of the linearly compensated diffracted light intensity with the driving voltage level reaches 97.85%,which is6.27% higher than before.In the heterodyne interferometer system,the error of demodulation signal after digital voltage modulation is only 1.3%,and the signal-to-noise ratio is up to30.29 dB.As for voice-signal communication,the acousto-optic modulator is well driven by the digital driving power.The linear modulation of the signal can be well achieved.When the TTL signal of 2kHz is transmitted,the linear correlation coefficient between the demodulated and the original is 0.8831.In the further research,it is necessary to refine the hierarchy so that the linearity of the drive power can adapt the higher precision technical requirements better.