基于激光自稳频技术的分布式多点甲烷检测系统研究

摘要

In order to ensure the long-term stability of laser methane detection system,achieve automatic calibrate function and significantly reduce the cost of point laser methane system,the distributed multi-point laser methane detection system by laser self-stabilizing technology was developed.Through the combination of hardware and software to achieve laser self-stabilizing technology,1/8 optical beam splitter was used to divide the light emitted by the laser into 8 channels,in which a reference chamber with constant methane gas was introduced.The second harmonic waveform of methane absorptive signal was obtained by real-time signal acquiring and processing.The wavelength and working range of laser wave were extracted.And then through the closed-loop negative feedback control link on the laser drive current automatically adjusted.Experimental results show that at the center of absorptive waveform,the wavelength control accuracy is 0.000 1 rnm,the wavelength fluctuating range from 1 653.697 5-1 653.749 6 nm is reduced to 1 653.723 4-1 653.723 6 nm,the working spectrum fluctuating range from 0.138 1-0.159 6 nm is reduced to 0.149 5-0.150 8 nm,the system detection error from the original ±4％ is reduced to ±0.5％.Based on laser self-stabilizing technology,the distributed multi-point laser methane system can realize a real-time monitoring of methane in multiple channels,the measurement error is less than 1％.With the laser self-stabilizing technology,the system can realize the precise control of laser working wavelength,and then ensure the long-term stability of laser methane detection system's performance during the environment temperature change and device aging.%为保证激光甲烷检测系统的长期稳定性,实现自动校准功能,同时大幅降低点式激光甲烷系统的成本,采用激光自稳频技术研发分布式多点激光甲烷检测系统.通过软硬件结合的方式实现激光自稳频,采用1/8光分束器将激光器出射光波分为8路,其中一路引入密封有恒定甲烷气体的参考气室,通过实时信号采集和处理得到甲烷吸收信号的二次谐波波形,提取出光波中心波长λ1和工作范围△λ1,再通过闭环负反馈控制链路对激光器驱动电流进行自动调节.实验结果表明:在吸收波形中心位置处,波长控制精度达到0.000 l nm,中心波长波动范围由1 653.697 5 ～1 653.749 6 nm减小至1 653.723 4～1 653.723 6 nm,波长工作光谱范围变化由0.138 1～0.159 6 nm减小至0.149 5～0.150 8 nm,将系统检测误差由原来的±4％减小至±0.5％;基于激光自稳频技术设计的分布式多点激光甲烷系统,能够实现多个测点甲烷的实时监测,其测量误差≤1％.采用激光自稳频技术,可以实现系统中工作波长的精确控制,进而保证激光甲烷检测系统在环境温度变化、器件老化等过程中性能的长期稳定性.