摘要
该文设计了基于全光学光声光谱技术的小型化医用呼吸气检测教学实验装置,该装置由分布反馈式半导体激光器、光纤声波传感器和T型共振式光声池组成。两个分布反馈式半导体激光器的中心波长分别对应甲烷和氨气的吸收峰,调制频率分别对应光纤声波传感器的共振频率和T型共振式光声池的共振频率。采用波分复用技术将两束激励激光耦合射入T型共振式光声池,由于光声效应产生的双频光声信号被光纤声波传感器所探测,实现甲烷和氨气的同时测量。经测试,实验装置检测时所需气量低、检测速度快,适合用于实验教学。
[Objective]Photoacoustic spectroscopy-based trace gas detection technology is known for its high sensitivity and rapid response times.The all-optical photoacoustic spectroscopy technique,which replaces traditional capacitive acoustic sensors with fiber-optic microphones,offers a compact design,enhanced sensitivity,an improved signal-to-noise ratio,and broader application possibilities.Given that exhaled breath contains trace gases associated with various diseases,researchers are actively working to accelerate detection times and enhance efficiency,thereby advancing multigas real-time monitoring techniques.[Methods]This study presents the design of a compact teaching experimental apparatus for medical exhaled gas detection using all-optical photoacoustic spectroscopy.The apparatus is designed to measure the methane and ammonia concentrations in human exhalation;it comprises distributed feedback semiconductor lasers,a fiber-optic acoustic sensor,and a T-type resonant photoacoustic cell.The cantilever beam in the fiber-optic sensor plays a critical role in device performance.Computational simulations were used to determine the cantilever beam’s optimal dimensions as 1.3 mm in length,0.8 mm in width,and 3.9μm in thickness,with a 5μm gap and a resonance frequency of 3,200 Hz.The central wavelengths of the two distributed feedback semiconductor lasers were set at 1,653.7 nm and 1,531.5 nm,corresponding to the absorption peaks of methane and ammonia,respectively.The laser modulation frequencies were tuned to match the resonance frequencies of the fiber-optic acoustic sensor and the T-type resonant photoacoustic cell.Wavelength-division multiplexing was employed to couple the two laser beams into the photoacoustic cell,where the fiber-optic acoustic sensor detected dual-frequency photoacoustic signals generated by the photoacoustic effect.Data processing was handled using LabVIEW to extract concentration information,enabling simultaneous measurement of methane and ammonia.Prior to experimentation,the laser’s modulation frequencies were calibrated by measuring the resonance frequencies of the photoacoustic cell and acoustic sensor.Nitrogen was utilized to establish gas concentrations,allowing the relationship between gas concentrations and photoacoustic signals to be determined,which subsequently facilitated sensitivity calculations.When used,students exhaled into the system via a water-resistant device.The system measured methane and ammonia concentrations in real time and yielded experimental results.[Results]The experimental system demonstrated detection limits of 0.31μL/L for methane and 45 nL/L for ammonia,meeting warning thresholds for a healthy physiological state.If ammonia concentrations fell outside the range of 200~1,750 nL/L,the LabVIEW interface displayed a warning prompt:“Abnormal ammonia concentration.”Similarly,methane concentrations exceeding 3μL/L triggered the prompt“Abnormal methane concentration.”When both gases were within normal ranges,the system displayed“Healthy.”Experimental validation confirmed that the system accurately displayed these results following exhalation.[Conclusions]The experimental system described herein enables real-time measurement of methane and ammonia in human exhaled breath.With its compact size,minimal gas requirements,and rapid detection capabilities,this system is well-suited for experimental teaching applications,achieving the anticipated design objectives.
作者
宫振峰
张馨予
梅亮
GONG Zhenfeng;ZHANG Xinyu;MEI Liang(School of Optoelectronic and Instrumentation Science,Dalian University of Technology,Dalian 116024,China)
出处
《实验技术与管理》
北大核心
2025年第5期155-160,共6页
Experimental Technology and Management
基金
国家自然科学基金项目(62375035)
大连理工大学教育教学改革基金项目(YB2024018)。
关键词
全光学光声光谱
呼吸气检测
光纤声波传感器
实验教学
all-optical photoacoustic spectroscopy
breath gas detection
fiber-optic acoustic sensor
experimental teaching
