| Wavelength modulation spectroscopy(WMS)is one of the important means of gas trace detection.However,we have to measure the laser intensity fluctuation,the intensity modulation response,current-scanning wavelength response and current modulation wavelength response to simulate the line shape of WMS.Current modulation wavelength response signal simulation especially increases the complexity of WMS technology application.At present,there are three different expressions with unknown parameters to describe the current modulation wavelength response(CMWR)and the unknown parameters should be determined by fitting the WMS signal.In order to simplify the description,a novel method based on the current modulation wavelength response(CMWR)is presented.More detailed contents are descripted as follow:(1)A new method to determine the CMWR of DFB laser is putted forward.Compared with traditional methods,the proposed method shows higher accuracy and precision.The advantages of the proposed method are:1)It avoids determining the unknown parameters of the expressions of constant modulation amplitude method,the first derivative method and the second harmonic method by the fitting process,and simulates the CMWR without direct measurement,and achieves the aim of free parameter fitting.2)The accuracy of CMWR is higher than that of constant modulation amplitude method and first derivative method,which reduces the complexity of measurement process and simplifies the experimental operation.3)It can be used to CF-WMS technique.(2)A CF-WMS experimental system was designed and constructed.We introduced the proposed method of determining the CMWR into the CF-WMS technique,and designed the dual channel digital lock-in amplifier and filter to demodulate the signal by use of Labview software.Based on the 1528nm DFB laser,the concentration of trace acetylene was detected and monitored by CF-WMS technique,and the accuracy and feasibility of the proposed method were further verified. |
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