| The resonant fiber optic gyroscope is a high precision inertial sensor based on the Sagnac effect.The light source is one of the key components,and it has an irreplaceable role.At the same time,the semiconductor laser is a sensitive component.The small changes in the injection current and the control temperature will cause the fluctuation of the laser output.In addition,laser drivers in developed countries are generally bulky and expensive,which is not conducive to the current product development of resonant fiber optic gyroscopes.Therefore,it is of great significance to design and develop a semiconductor laser drive system with good performance,small size and low price.In this paper,the design of laser drive system is mainly for current drive and temperature control.Firstly,the main working process of the semiconductor laser and two main factors affecting the output stability of the laser are analyzed from the principle and working characteristics of the laser:current and temperature.Secondly,the basic laser driving principle and the constant temperature principle are analyzed.In the current control,the constant current drive control is selected after comparing the three driving modes of constant current driving,constant power driving and pulse driving.In the aspect of temperature control,several temperature control schemes commonly used by mainstream research institutions were compared,and the temperature control design scheme based on MAX1978 chip was selected.In this paper,the current control and temperature control circuits are designed for the characteristics of semiconductor lasers,and the system is digitally closed-loop controlled by FPGA to improve the stability of the system.In the current driving process,the D/A module outputs a control voltage signal through the FPGA,and the three signals of the bias signal,the modulation signal,and the scan signal can be applied to the laser alone or superimposed on the laser through the adding circuit.In the constant current output control part,deep negative feedback and PID dual control are used to improve the output current stability,so that the constant current output is 69ppm.In terms of constant temperature control,using the mature temperature control chip MAX1978,the maximum temperature fluctuation can be achieved within 0.003?,and the stability is 0.0125%.The accuracy of the DA output is approximately equal to the tuning accuracy,which can be up to7×10-5,and the output rising edge time is approximately representative of the tuning,and the tuning time is 1.15?s.Based on the laser drive control system,the maximum measurement power deviation is 0.0024mW,and the stability is 0.073%,which is about 13 times higher than the purchased RIO laser module.Between the input voltage is 1V to 3V,the output power and the input voltage have a good linear relationship.The output laser wavelength is stable around 1550nm,the fluctuation error is within 0.001nm,and the stability is 0.645ppm,which is 4 times higher than the purchased module.The output wavelength and input voltage are linear between 1V and 3.5V input voltage.The system is docked with the existing gyro system in the laboratory,and the performance of the system is judged by the resonance curve.The full width at half maximum is about 350 kHz,the free spectral width is 15.4 MHz,the fineness is 44,and the resonance depth is 0.95.It can be seen that the design driver of this paper satisfies the design requirements of the resonant fiber optic gyroscope.Through the final system verification,the design of the resonant fiber-optic gyro source drive can effectively drive the RIO laser,and the final output current and temperature stability is good.It can meet the performance requirements of the resonant fiber-optic gyroscope while still meeting the miniaturization integration requirements. |
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