Temperature and concentration measuring system and method based on double-optical-comb spectrum technology

Abstract

The invention provides a temperature and concentration measuring system and method based on a double-optical-comb spectrum technology, and belongs to the technical field of laser absorption spectra. The measuring system comprises two optical frequency combs with the repetition frequency difference smaller than 1 MHz, a 2*2 optical fiber coupler, an optical band-pass filter, a collimator, a low-pass filter, a photoelectric detector, a data acquisition card and the like. The double optical combs are subjected to coupling beam splitting, one path is a measurement light path and is received by thephotoelectric detector after passing through to-be-measured gas and the optical band-pass filter, and the other path is a reference light path and is coupled to the photoelectric detector after passing through the optical band-pass filter. Interference signals generated by the double optical combs on the photoelectric detector are filtered by the low-pass filter and then acquired by the data acquisition card. Fourier transform is carried out on interference signals of measurement and reference light paths to extract absorption spectrum information. Finally, the temperature and the concentration are calculated based on a polychromatic method and a least square method. According to the invention, the precise spectral resolution capability of the optical frequency combs is utilized to realize wavelength-free calibration measurement of temperature and concentration, and the application prospect is wide.

Description

technical field [0001] The invention relates to a temperature and concentration measurement system and method based on dual optical comb spectrum technology, which belongs to the technical field of laser diagnosis. The system is used for quantitative measurement of temperature and specific molecular concentration on a laser path. Background technique [0002] As a non-contact measurement method with fast response, high sensitivity and anti-interference, gas parameter measurement technology based on laser absorption spectroscopy has been developed rapidly in recent years, and is widely used in combustion diagnosis, atmospheric monitoring, industrial sites and other fields. [0003] Traditional laser absorption spectroscopy mainly uses tunable diode laser absorption spectroscopy (TunableDiode Laser Absorption Spectroscopy, TDLAS). The wavelength scanning range of the tunable diode laser used in TDLAS technology is limited, and generally only covers one or two characteristic ab...

AI Technical Summary

Problems solved by technology

In 2009, G.B.Rieker et al. published the paper "Measuring Gas Temperature and Concentration Using Calibration-free Wavelength Modulation Spectroscopy in Harsh Environments" (Calibration-free wavelength -modulation spectroscopy for measurements of gastemperature and concentration in harsh environments) in testing the temperature of scramjet exhaust port, CO 2 、H 2 In the process of O concentration, six DFB lasers with different bands are used. After the grating is split, multiple detectors are used to receive laser signals of different bands, which increases the complexity of the system.

The high-degree polynomial fitting baseline method used in this paper has a poor fitting effect when the spectral shape of the optical frequency comb is not flat enough or there is serious distortion. In addition, when the absorption intensity is high, the weak absorption on both wings of the absorption peak is not good for baseline fitting

At the same time, the multi-spectral fitting method needs to adjust the fitting parameters related to the absorption spectrum, such as temperature, concentration, and pressure, which increases the computational burden and the complexity of data processing, and is sensitive to background noise.

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